Acoustic Guide

G U I D E

ACOUSTIC Insulation Design Guide

A C O U S T I C

D E S I G N

A C O U S T I C

D E S I G N

Introduction.

Contents.

The Bradford Insulation Group forms part of the Building Materials Division of CSR Limited. CSR Bradford Insulation manufactures and markets an extensive range of insulation products offering outstanding thermal, acoustic and fire protection properties for use in all types of domestic and commercial buildings. Two mineral fibre insulation types are available; ‘Bradford Glasswool’, which is manufactured by controlled felting of biosoluble glass wool bonded with a thermosetting resin; and ‘Bradford Fibertex™ Rockwool’ which is spun from natural rock and bonded with a thermosetting resin. Both are available in sheet or roll form and as moulded pipe insulation. Bradford Thermofoil™ and Thermotuff™ are a range of aluminium foil laminates available in various grades. All CSR Bradford Insulation products are tested to meet stringent quality control standards incorporating quality management systems such as AS3902/ISO9002.

2

Introduction Product Range, Applications & Selection Guides

3 – 13

Bradford Acoustic Solutions Party & Interior Walls Residential & Commercial External Walls Roof/Ceiling Systems Floor/Ceiling Systems Floors Plumbing Gutters & Downpipes Pipes, Tanks & Vessels Factories & Workshops Acoustic Baffles Acoustic Enclosures Vibration Damping Air Conditioning Systems

14 18 18 23 24 25 26 27 27 29 30 34 36

ABOUT THIS GUIDE. The purpose of this guide is to provide information on the technical benefits obtained with the inclusion of acoustic insulation materials in the construction of all types of buildings as well as noise control of machinery. The range of Bradford products and their applications is presented along with data and worked examples to illustrate design considerations. This Acoustic Design Guide also outlines the basic properties of sound, and methods for its control. It does not set out to provide a definitive solution to every conceivable noise problem. Rather, it aims to explain the principles involved, so that these principles can be applied along with common sense, to overcome common acoustic problems. Acoustics is however a complex science, and there will be many instances where the services of specialist acoustic consultants or noise control engineers are indispensable. The reader is cautioned against investing large sums of money in noise control without first seeking advice. This is particularly pertinent where compliance with noise abatement orders is concerned.

Bradford Acoustic Solutions for Specialty Applications Home Cinema Auditoriums Sports Complexes Canteens/Restaurants Karaoke/Night Clubs Shopping Centres Recording Studios Heavy Plant OEM Application Appendix A

The Nature of Sound Sound Transmission Flanking Paths Sound Absorption Reverberation Room Acoustics Industrial Acoustics Speech Privacy

46 47 48 50 50 51 52 53 53 54 57 59 59 61 64 67 68

Appendix B

Floor/Ceiling Systems

Appendix C

Product Data Sound Absorption Coefficients Static Insertion Loss/Silencers Air Flow Resistivity

71 74 77 78

Appendix D

Terminology

79

CSR Bradford Insulation Regional Contact Details

G U I D E

TECHNICAL ASSISTANCE. To assist designers, a free and comprehensive technical service, as well as advice and assistance in specifying and using Bradford products is available from CSR Bradford Insulation offices in your region. Further technical data and product updates are also available on the CSR Building Solutions Website: www.csr.com.au/bradford Information included in this Design Guide relates to products as manufactured at the date of publication. As the CSR Bradford Insulation policy is one of continual product improvement, technical details as published are subject to change without notice.

69 – 70

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CSR BRADFORD INSULATION

A C O U S T I C

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G U I D E

The Importance of Acoustic Insulation. The minimisation of noise has become a significant environmental issue in the modern world, whether at home, at work or on holidays. CSR Bradford Insulation manufacturers and distributes an extensive range of insulation products that provide excellent noise control properties, as well as the traditional thermal and fire control benefits. Although all fibrous insulation products can provide some acoustic benefits, CSR Bradford Insulation has a range of products specifically designed and tested for the acoustic insulation market, including:–

ACOUSTIC INSULATION PRODUCT

APPLICATIONS

Bradford Glasswool Partition Batts

Economical insulation for internal wall sound absorption in housing, residential apartments or commercial offices. Various systems are available to meet building codes.

Bradford SoundScreen™

Unique rockwool insulation system to reduce room-toroom noise transmission in houses.

Bradford ACOUSTICON™

Commercial and residential metal roofing insulation specially developed to reduce rain noise.

Bradford Glasswool R1.5 ACOUSTITUFF™ Ductliner

Air conditioning duct internal lining product offering full enclosure with excellent sound absorption properties.

Bradford Glasswool R1.5 ULTRAPHON™ Ductliner

High performance acoustic absorption product for ducting, silencers and other acoustic applications.

Bradford ACOUSTICLAD™

Wall absorber combining the superior acoustic properties of Bradford Fibertex™ Rockwool with a perforated metal panel system.

Bradford Glasswool ACOUSTILAG™

Pipe insulation product combining the noise barrier properties of loaded vinyl and the absorption benefits of glasswool. Ideal for noisy plumbing.

Bradford FIBERTEX™ Acoustic Baffle

Rockwool batt enclosed in white polymer film used for which is designed to be hung from the overhead structure to provide acoustic absorption in a room or workplace.

Bradford Glasswool SUPERTEL™

General purpose medium density glasswool acoustic insulation.

Bradford Rockwool FIBERTEX™ 450

General purpose premium rockwool acoustic insulation product.

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Acoustic Insulation for Homes.

1

Metal Roof Insulation or Tiled Roof Sarking

2

Ceiling Insulation

3

Internal Wall Insulation

4

External Wall Insulation/ Party Wall

5

Plumbing Insulation

6

7

Acoustic Floor/Ceiling & Floating Floor Insulation

Home Cinema Wall, Floor & Ceiling Insulation. Acoustic Absorbing Panels

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Bradford Insulation Application & Selection Guide for Homes. Insulation Application

1

3 4 5 6

Ceiling

Acoustic Internal Walls

External Walls

Plumbing

Acoustic Floor/Ceilings

Floating Floors

7

Product Range/Facings

Bradford ACOUSTICON™ Blanket

Medium, Heavy Duty or Specialty THERMOFOIL™

Bradford Glasswool ANTICON™ Blanket

R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL™

Bradford FIBERTEX™ Rockwool ANTICON™ Blanket


Bradford THERMOFOIL™ Sarking

Medium, Heavy Duty, ANTIGLARE

Bradford THERMOTUFF™ Sarking

Medium, Extra Heavy Duty, Safety

Bradford Glasswool Gold Ceiling Batts

R2.0, R2.5, R3.0, R3.5, R4.0

Bradford FIBERTEX™ Rockwool Ceiling Batts

R2.0, R2.5, R3.0

Metal Roofing

Tiled Roof Sarking

2

Product Type

Home Cinema

Bradford ACOUSTILAG™

2.5 - 5.0mm Loose Fill Bags


50, 75 and 100mm

Bradford Rockwool SoundScreen™

75mm

Bradford Glasswool Gold Wall Batts

R1.5, R2.0

Bradford FIBERTEX™ Rockwool Wall Batts

R1.5, R2.0

Bradford FIBERTEX™ Rockwool Cavity Wall Granulated

Loose Fill Bags

Bradford ACOUSTILAG™ Pipe Insulation

ACOUSTILAG™ 20, 23 and 26

Bradford HANDITUBE™ Pipe Insulation

Stocked by CSR Bradford Insulation


R1.5 - R2.0

Bradford Glasswool Wall/Floor Batts

R1.5 - R2.0

Bradford FIBERTEX™ Rockwool Wall/Floor Batts

R1.5 - R2.0


75mm

Bradford Glasswool QUIETEL™

Specialty installation system


Specialty facings available

Bradford FIBERTEX™ Rockwool

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Acoustic Insulation for Homes.

1 2

Tiled Roof Sarking or Metal Roof Insulation

Ceiling Insulation

3

Internal Wall Insulation

4

External Wall Insulation

5

Plumbing Insulation

6

7

Acoustic Floor/Ceiling & Floating Floor Insulation

Home Cinema Wall, Floor & Ceiling Insulation. Acoustic Absorbing Panels

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Bradford Insulation Application & Selection Guide for Homes. Insulation Application

1

3 4 5 6

Ceiling


External Walls

Plumbing

Acoustic Floor/Ceilings

Floating Floors

7


Bradford ACOUSTICON™ Blanket

Medium, Heavy Duty or Specialty THERMOFOIL™

Bradford Glasswool ANTICON™ Blanket


Bradford FIBERTEX™ Rockwool ANTICON™ Blanket


Bradford THERMOFOIL™ Sarking

Medium, Heavy Duty, ANTIGLARE

Bradford THERMOTUFF™ Sarking

Medium, Extra Heavy Duty, Safety

Bradford Glasswool Gold Ceiling Batts

R2.0, R2.5, R3.0, R3.5, R4.0


R2.0, R2.5, R3.0

Bradford ACOUSTILAG™

25mm – 50mm


50, 75 and 100mm


75mm

Bradford Glasswool Gold Wall Batts

R1.5, R2.0

Bradford FIBERTEX™ Rockwool Wall Batts

R1.5, R2.0

Bradford FIBERTEX™ Rockwool Cavity Wall Granulated

Loose Fill Bags

Bradford ACOUSTILAG™ Pipe Insulation

ACOUSTILAG™ 20, 23 and 26

ARMAFLEX™ Pipe Insulation

Stocked by CSR Bradford Insulation


R1.5 - R2.0

Bradford Glasswool Wall/Floor Batts

R1.5 - R2.0

Bradford FIBERTEX™ Rockwool Wall/Floor Batts

R1.5 - R2.0


75mm


Specialty installation system



Metal Roofing

Tiled Roof Sarking

2

Product Type

Home Cinema


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Acoustic Insulation for Commercial Buildings

7

Air Conditioning Duct Insulation (Rigid & Flexible Ducts)

6

Fan Silencer & Fan Casing Insulation

1

Ceiling Insulation (Suspended Grid Ceilings & Concrete Roof/Soffit)

2

Internal Partition Wall Insulation

3

Acoustic Absorbing Panels

4

Plumbing Insulation

5

Plant Room Wall & Ceiling Insulation

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A C O U S T I C

D E S I G N

G U I D E

Bradford Insulation Application & Selection Guide for Commercial Buildings. Insulation Application

Product Type


Bradford Glasswool ANTICON and ACOUSTICON™ Blanket

™

1

Concrete Roof/Soffit

Bradford FIBERTEX™ Rockwool ANTICON™ Blanket Bradford Glasswool SUPERTEL™ Bradford FIBERTEX™ 350 Rockwool

Exposed Grid Ceiling Concealed Grid Ceilings

2

Acoustic Internal Partitions

3


4

Plumbing Insulation

5

Plant Room Wall & Ceiling Insulation

6

Fan Casings

Fan Silencers

7

Rigid Ducting Internal Lining

Rigid Ducting External Wrap

Flexible Duct

Bradford Glasswool Ceiling Panel Overlays Bradford FIBERTEX™ Rockwool Ceiling Panel Overlays Bradford Glasswool Building Blanket Bradford FIBERTEX™ Rockwool Building Blanket Bradford Glasswool Partition Batts Bradford FIBERTEX™ Rockwool Partition Batts Bradford Glasswool ULTRATEL™ Board Bradford FIBERTEX™ 450 Rockwool Bradford ACOUSTILAG™ Pipe Insulation ARMAFLEX™ Pipe Insulation Bradford Rockwool/Glasswool ACOUSTICLAD™ Bradford Glasswool FLEXITEL™, SUPERTEL™, ULTRATEL™ Bradford FIBERTEX™ 350 Rockwool

R1.5, R2.0, R2.5 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL™ R1.5, R2.0 Faced Light, Medium, Heavy Duty or Specialty THERMOFOIL™ 25 – 75mm THERMOFOIL™ Facing 50 - 100mm THERMOFOIL™ Facing Factory Applied Acoustic Facings Factory Applied Acoustic Facings R1.2, R1.5, R1.8, R2.0, R2.5 50, 75mm, R1.5, R2.0 50, 75, 100mm 45, 70mm 25-100mm, Factory Applied Facings 25-100mm, Factory Applied Facings ACOUSTILAG™ 20, 23 and 26 Stocked by CSR Bradford Insulation Perforated 750P THERMOFOIL™ Perforated 750P THERMOFOIL™ Perforated 750P THERMOFOIL™ ACOUSTITUFF™ ULTRAPHON™ BMF, ULTRAPHON™ 25 – 100mm (Quietel 13mm - 50mm)

Bradford Glasswool FLEXITEL™ Bradford Glasswool SUPERTEL™ Bradford Glasswool QUIETEL™ Bradford FIBERTEX™ Rockwool DUCTLINER Bradford Glasswool SUPERTEL™ Bradford Glasswool ULTRATEL™ Bradford Glasswool QUIETEL™ Bradford FIBERTEX™ Rockwool DUCTLINER Bradford FIBERTEX™ 450 Rockwool Bradford Glasswool SUPERTEL™ Perforated 750P THERMOFOIL™ Bradford Glasswool DUCTLINER ULTRAPHON™, Bradford Glasswool ULTRATEL™ ACOUSTITUFF™ facings ™ Bradford FIBERTEX Rockwool DUCTLINER 25 – 100mm, R1.5 & R0.9 ™ Bradford Glasswool MULTITEL R1.5 & R0.9 Bradford Glasswool FLEXITEL™ 25 – 100mm ™ Bradford Glasswool THERMOGOLD DUCTWRAP Bradford FIBERTEX™ Rockwool DUCTWRAP Bradford Glasswool R1.0 SPECITEL™ R1.0. R1.5 Bradford FABRIFLEX™ Flexible Ducting Available ex-Singapore ™ Bradford ACOUSTIFLEX Flexible Ducting Available ex-Singapore

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Acoustic Insulation for Theatre, Sports & Multi-Purpose Buildings

1

Auditorium/Theatre/Cinema • Roof/Ceiling Insulation • Wall Insulation • Acoustic Absorbing Panels

2

Sports Centre • Roof/Ceiling Insulation • Floor Insulation • Acoustic Absorbing Panels

4

Air Conditioning System Insulation

3

Canteen • Wall Insulation • Ceiling Insulation • Acoustic Absorbing Panels • Metal Deck Rain Noise Insulation

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Bradford Insulation Application & Selection Guide for Theatre, Sports & Multi-Purpose Buildings. Insulation Application Walls

Product Type Bradford Glasswool Partition Batts Bradford Rockwool Partition Batts

Acoustic Absorbers

1

Bradford Glasswool FLEXITEL™, SUPERTEL™ ULTRATEL™ with BMF (Black Matt Facing Tissue), ULTRAPHON™ or other specialty facing. Bradford FIBERTEX™ Rockwool Bradford ACOUSTICLAD Wall/Ceiling Absorber

Theatre, Cinema & Auditorium

Roof/Ceiling Bradford Glasswool ACOUSTICON™ Bradford Glasswool Ceiling Batts Bradford Rockwool Ceiling Batts Acoustic Absorbers

2

Sports Buildings • Swimming • Basketball • Gymnasium

Bradford ACOUSTICLAD™ Wall/Ceiling Absorber Bradford FIBERTEX™ Rockwool Bradford Glasswool FLEXITEL™, SUPERTEL™ ULTRATEL™ with BMF (Black Matt Facing Tissue), ULTRAPHON™ or other specialty facing. Roof/Ceiling Bradford Glasswool ACOUSTICON™ Bradford Glasswool Ceiling Batts Bradford Rockwool Ceiling Batts Acoustic Absorbers

3

Canteen Facility

Bradford FIBERTEX™ Rockwool Bradford Glasswool FLEXITEL™, SUPERTEL™ ULTRATEL™ with BMF (Black Matt Facing Tissue), ULTRAPHON™ or other specialty facing. Bradford ACOUSTICLAD Wall/Ceiling Absorber Walls Bradford Glasswool Partition Batts Bradford Rockwool Partition Batts Roof/Ceiling

4

Air Conditioning Systems

Bradford Glasswool ACOUSTICON™ Bradford Glasswool Ceiling Batts Bradford Rockwool Ceiling Batts Refer to CSR Bradford Insulation Air Conditioning Design Guide and Product Guide.

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Acoustic Insulation for Industrial Applications.

2

Acoustic Enclosures for Plant & Machinery

1

Acoustic Baffles (suspended)

8

Acoustic Wall Absorbers

7

Metal Deck Roof Insulation

6

Ceiling Insulation

3

Bradford Insulation for OEM Applications

5

Acoustic Internal Wall Insulation

4

Acoustic Absorbing Screens

12


A C O U S T I C

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G U I D E

Bradford Acoustic Insulation for Industrial Applications. Insulation Application

1 2

Acoustic Baffles

Product Type


Bradford FIBERTEX™ Acoustic Baffle

Fully enclosed in white polymer film ready to hang.

Acoustic Enclosures for Plant & Machinery


25 – 100mm

Bradford Glasswool FLEXITEL

Density 24 – 120kg/m3

™

Bradford Glasswool SUPERTEL™ Bradford Glasswool ULTRATEL™

3

OEM Applications

Bradford Glasswool Appliance Grade

Cut to size with specialty facings

Bradford Rockwool Appliance Grade

available

Bradford Glasswool QUIETEL

™

4

Acoustic Absorbing Screens


25 – 100mm

5



6

Ceilings

7

Metal Deck Roofs

Bradford Glasswool ACOUSTICON™

8

Acoustic Wall Absorbers

Bradford ACOUSTICLAD™

25 – 100mm



Bradford FIBERTEX™ Rockwool To fit studs

Bradford FIBERTEX Rockwool Partition Batts ™

Bradford Glasswool Ceiling Batts

50 – 150mm

Bradford Rockwool Ceiling Batts 75mm

Bradford Rockwool ACOUSTICON

™

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Bradford Acoustic Solutions. Interior Walls.

The addition of denser wall sheeting products such as CSR Gyprock® Fyrchek™ or Soundchek™ plasterboard or CSR Fibre Cement together with Gyprock’ Resilient Mounts and furring channels can reduce noise levels.

RESIDENTIAL PARTY & INTERNAL WALLS. The Building Code of Australia (BCA) Sections F5 sets out Sound Transmission Class (STC) requirements for sound insulation of floors, walls, between units, walls between bathrooms, laundries, kitchens, between habitable and non-habitable rooms in multi-tenancy buildings. In late 1999, the BCA changed its acoustic rating from STC to Sound Reduction Index (Rw). This Acoustic Design Guide uses the STC rating units as Australasia and Asia are familiar with STC and it is very similar to Rw. An increase of either one STC unit or one Rw unit approximately equals a reduction of one decibel in noise level. Table 1 below shows common STC values of walls used in buildings. The expected audibility for a given STC level is also shown, based on guidelines for ambient sound levels

DOUBLE-LEAF WALLS. Higher transmission losses than those expected by the Mass Law can be obtained by using double-leaf walls with an air cavity. Further increases in sound transmission loss, particularly at low frequencies can be achieved by using wider air cavities. When a double leaf wall is uninsulated, the air in the cavity can act as a spring, efficiently transmitting sound energy from one side of the wall to the other. Significant improvement in STC is obtained by using Bradford Rockwool or Glasswool batts in the cavity. Acoustic tests of walls around the world have shown the use of glasswool batts or rockwool batts inside cavity walls reduces resonances between the two sheets and can significantly improve the acoustic performance by up to 10 STC. Generally the thicker and/or denser the insulation in the cavity, the higher the STC rating resulting in less noise transmitted to the other side of the wall. The actual improvement in STC depends on the type of wall construction. Insulation in the cavity will also lessen the effect of the ‘coincidence dip’ in double leaf walls.

TABLE 1. STC AND AUDIBILITY THROUGH WALLS AND FLOORS. STC Value

Audibility

30 - 35

Speech audible

40

Loud speech, still heard

45

Loud speech, just heard

50 – 55

Speech cannot be heard

The BCA Part F5.4 Sound Insulation Of Walls Between Units currently states a wall must have an STC not less than 45. It has been proposed to increase this to STC 55 in the future as STC 45 does not provide enough acoustic privacy. STC’s ≥50 are standard in Europe and USA.

FLANKING NOISE. It should be noted that actual installations, as compared to acoustic laboratories, exhibit flanking noise through doors, windows, ventilation ducting, air gaps at ceiling, wall and floor intersections. In addition, poor workmanship may degrade the acoustic performance of partitions. For these reasons, a building element constructed in the field will usually achieve a lower STC ratings than when tested in the laboratory. Maximum acoustic performance can be achieved by eliminating penetrations in walls, caulking gaps, and staggering electrical outlet or other necessary penetrations through the wall. Wall cavities should be completely filled with insulation and tightly fitted around pipes, conduits and other outlets.

Generally internal walls for residential applications in Australia use either rendered brick or lightweight double leaf walls using plasterboard and/or fibre cement construction on timber studs. To improve or increase the sound transmission loss (STL) hence the STC of these walls, the following is required:-

EXTRA MASS. Sound Transmission Loss (STL) depends heavily on the surface density of a building element (mass per square metre of surface). For every doubling of surface density, the sound transmission loss increases by about 5dB.

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STC data for some typical partition walls is given in Table 2. Further STC data for internal cavity walls is available the CSR Bradford brochure ‘Noise Reductions For Internal Partitions or the CSR Gyprock Fire & Acoustic Design Guide, ‘The Red Book’.

LOW FREQUENCY NOISE. Low frequency noise from sources such as fans, aircraft, road and rail traffic, and bass from amplified music can penetrate walls easier than high frequency noise. Therefore higher sound transmission loss (ie. higher STC) walls are required to ensure satisfactory acoustic performance. As a general rule, add at least 5 STC points to the acoustic requirement of the walls when low frequency noise is present.

TABLE 2. STC DATA FOR TYPICAL TIMBER FRAME PARTITION SYSTEMS.

Description

STC (Rw) No Insulation 33

STC 30 - 42 • 1 layer 10mm CSR Gyprock Plasterboard CD™ • 70/75mm Timber Studs • 1 layer 10mm CSR Gyprock Plasterboard CD™

STC (Rw) Bradford Glasswool Wall Batts

STC (Rw) Bradford Rockwool Wall Batts

38 (75mm Batts)

39 (45mm Batts) Test CSR 37/67

42 SoundScreen™

STC 40 - 50 • 2 layers 13mm CSR Gyprock Fyrchek™ plasterboard • 70/75mm Timber Studs • 1 layer 13mm CSR Gyprock Fyrchek™ plasterboard STC 50 - 60 • 2 layers 16mm CSR Gyprock Fyrchek™ plasterboard • 90 x 35mm Staggered Timber Studs • 2 layers 16mm CSR Gyprock Fyrchek™ plasterboard

43

47 (50mm Batts)

48 (45mm Batts)

51

58 (50mm Batts)

59 (45mm Batts)

* Refer to the CSR Bradford Noise Reduction of Internal Partitions brochure or the CSR Gyprock® Fire & Acoustic Design Guide (‘The Red Book’) which show a wide range of internal partitions and their STC ratings.

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COMMERCIAL INTERNAL PARTITIONS. Internal plasterboard or fibre cement walls using steel stud systems are widely used in commercial construction and offer a wide range of sound transmission loss performance.

Thinner gauge steel studs, with greater stud spacing and minimum fixing of sheets to studs also results in a wall which is able to flex more easily generally resulting in slightly higher acoustic performance.

The methods stated previously for improving acoustic performance of Residential Internal Walls also apply to the Commercial Internal Partitions.

If higher STC performance is required, there are a number of steps that can be incorporated at the time of construction to improve acoustic performance, as detailed in Table 3.

TABLE 3. INSULATION FOR NOISE REVERBERATION CONTROL. Addition

STC Improvement

Comments

Fit insulation into studs

Up to 10 STC points

Thicker and/or denser insulation such as Rockwool is beneficial. Light gauge or deeper steel studs give higher STC performance.

Use Gyprock® Fyrchek plasterboard

Up to 3 STC points if installed both sides

Use of 13mm or 16mm CSR Gyprock® Fyrchek™ improves performance due to extra mass.

Gyprock® Resilient Channel one side

6 – 8 STC points

Resilient Channel isolate the Gyprock® Plasterboard from the stud.

Bradford Quietel one side and insulation to stud

4 STC points

Quietel board acts as a sound isolator between the Gyprock® Plasterboard and the Stud.

Staggered and double studs

Up to 10 STC points

Provide sound breaks between solid studs and Gyprock®. Recommended where impact isolation is also required.

Gyprock® Resilient Mounts and Furring Channel

Up to 10 STC points

Used where high level reduction of airborne and impact noise is required.

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TABLE 4. STC RATINGS OF SOME COMMERCIAL INTERNAL PARTITIONS*. A sample of the STC ratings for commercial internal partitions using steel studs taken from the Tables in the CSR Bradford Insulation ‘Noise Reductions for Internal Partitions’ brochure, together with results from recent testing.

Description

STC (Rw) No Insulation

STC 30 - 40 • 1 layer 13mm Gyprock Plasterboard CD™ • 64mm Steel Studs • 1 layer 13mm Gyprock Plasterboard CD™

35

STC (Rw) Bradford Glasswool Partition Batts

STC (Rw) Bradford Rockwool Partition Batts

40 (50mm Batts)

41 (45mm Batts)

Test HAS 085

STC 40 - 50 • 1 layer 16mm Gyprock Fyrchek™ • 64mm Steel Studs • 1 layer 16mm Gyprock Fyrchek™ STC 50 - 60 • 1 layer 13mm Gyprock Fyrchek™ plasterboard • 64 x 0.75mm BMT Separated Steel Studs • 1 layer 13mm Gyprock Fyrchek™ plasterboard STC 55 - 60 • 1 layer 16mm Gyprock Fyrchek™ plasterboard • 64 x 0.75 BMT Separated Steel Studs • 1 layer 16mm Gyprock Fyrchek™ plasterboard STC 60 - 70 • 2 layers 16mm Gyprock Fyrchek™ plasterboard • 92 x 0.75mm BMT Separated Steel Studs • 2 layers 16mm Gyprock Fyrchek™ plasterboard

39

44 (50mm Batts)

45 (45mm Batts)

45

57 (75mm Wall Batts)

58 (75mm SoundScreen™)

45

55 (80mm Batts)

60 (75mm SoundScreen™)

55

63 (75mm Batts)

64 (70mm Batts)

* Refer to the CSR Bradford Insulation Noise Reduction of Internal Partitions brochure or CSR Gyprock® Fire & Acoustic Design Guide (‘The Red Book’) which show a wide range of internal partitions and their STC ratings.

ACOUSTIC PREDICTION SYSTEM. loss STC greater than 50, such as those used between recording studios or cinemas, flanking paths should be considered, as they can derate the acoustic performance of the partition. For cinema walls requiring a very high STC rating, contact CSR Bradford Insulation regarding the CSR Gyprock® Cinema Wall System, or other CSR systems.

CSR Bradford Insulation has available a sophisticated ‘Acoustic Predictor’ computer program, developed by CSR Gyprock®, which can predict the STC rating of many different internal partitions, in addition to those shown above and in the brochure. Note: For walls which require high sound transmission 17


A C O U S T I C

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External Walls.

G U I D E

To improve STC performance of single timber studs, consider the use of Rondo resilient channels or CSR Gyprock® resilient mounts with furring channels, which can improve STC (or Rw) by 6 to 8.

External walls of residential buildings usually consist of • brick veneer construction, or lightweight concrete construction,

Buildings with double brick walls should use vibration isolated wall ties to reduce the amount of noise and vibration transmitted from one wall to the other.

• a cladding material, usually timber or fibre cement or • occasionally double brick.

Note that building elements of low acoustic performance will derate the improvements made to other building elements ie. walls and ceilings. For example, lightweight windows and doors can reduce the overall STC rating of the wall.

For better acoustic performance, use building materials with more mass. Clay bricks provide high surface density (or mass per square metre) to enable high transmission loss. The use of CSR Gyprock® Soundchek™ or Fyrchek™ plasterboard is recommended for interior walls. For even higher wall STC, the use of CSR Gyprock® Resilient Mounts and Furring Channels is recommended.

Products. Bradford Glasswool Wall Batts Bradford Rockwool Wall and Ceiling Batts

For brick veneer walls add the thickest possible rockwool or glasswool batts inside wall cavities during construction of the building.

Roof/Ceiling Systems. Roof/ceiling systems generally consist of either steel roofing or tile roofing. These roofing systems usually provide average to poor acoustic performance and can be an acoustically weak link in a building facade. It should be noted that consideration should be given to other weak links in the building extensions such as windows and doors.

Granulated rockwool can be retro-fitted into existing walls of a building using a special machine which blows granulated rockwool under pressure into the wall cavities. Wall sheeting usually has solid connections (ie screw or nail fixed) to the timber or steel studs and transmits noise through these solid connections. CSR Gyprock® Resilient Mounts can reduce both noise and vibration transmission.

Low frequency noise generated by aircraft, road and rail traffic can easily penetrate commonly used building materials including the roofing.

FIG 1. EXTERNAL WALL INSULATION.

Tile roofs are generally used in domestic applications. It is recommended that Bradford Rockwool or Glasswool Ceiling Batts be used in the roof cavity to improve both acoustic and thermal resistance. Note the higher the thermal resistance or R-value, the thicker the batt, and the better the acoustic absorption. The following points indicate methods to improve the acoustic performance of a typical tiled roof system. Tips on how to further improve the STC rating are provided in (brackets)

Bradford Thermofoil or Thermotuff Breather

• Rockwool or glasswool insulation batts on top of the ceiling, (the thicker the insulation or the higher the R-rating, the better the acoustic absorption)

Timber Frame

• Using a heavy THERMOFOIL ™ sarking as a condensation barrier under the roof tiles, the heavier the better the noise reduction.

Bradford Insulation Wall Batts External Cladding

• Adding Bradford SOUNDLAGG™ loaded vinyl over the ceiling joists, (the heavier the better). • Thicker and/or heavier plasterboard for the ceiling, (use fire rated plasterboard and multiple layers). Care should be taken to minimise all gaps in the roof ceiling to maximise the acoustic performance.

Gyprock® Plasterboard

18


A C O U S T I C

D E S I G N

G U I D E

TILED ROOF SYSTEMS. rockwool or glasswool insulation will maximise noise absorption in the roof space, minimising the amount of noise entering the room/s below.

Figure 2 shows how to improve the acoustic performance of a typical tiled roof system. Note that the gaps inherent in tile roof construction allow noise to enter the roof cavity. Hence the use of

FIG 2. IMPROVING ACOUSTIC PERFORMANCE OF TILED ROOF SYSTEMS. Bradford Thermofoil 733 Sarking over rafters Monier Concrete Roof Tiles

STC/Rw

SYSTEM Monier concrete tile roof with one layer of Gyprock Supa-Ceil™ plasterboard fixed to ceiling joists spaced at 600mm centres.

33

Add Bradford R2.5 Glasswool Batts between joists.

41

Replace Bradford R2.5 Glasswool Batts with Bradford R3.0 FIBERTEX™ Rockwool Building Batts between joists, and install Bradford THERMOFOIL™ 733 over rafters.

45

Add Bradford SOUNDLAGG™ (6kg/m2) over ceiling joists.

50

Bradford Soundlagg (6kg/m2) over joists

Ceiling Joist Gyprock 10mm Supa-Ceil Plasterboard Ceiling

Bradford Glasswool or Rockwool Ceiling Batts (as indicated)

STEEL ROOFING SYSTEMS. installed directly underneath the metal decking to guard against condensation.

Steel roofing is used in both commercial and residential roofing systems in Australia, New Zealand and Asia.

Figure 3 shows the improvement in STC of a typical domestic roof with the addition of Bradford insulation in the roof/ceiling system.

Metal deck roofing systems require a layer of thermal insulation faced with a suitable vapour barrier to be

FIG 3. IMPROVING ACOUSTIC PERFORMANCE OF STEEL ROOF SYSTEMS.

SYSTEM

STC/Rw Metal Roofing

Metal roofing with 1 x 10mm Gyprock Supa-Ceil™ plasterboard fixed to ceiling joists spaced at 600mm centres.

34

Add Bradford ACOUSTICON™ foil faced building blanket over rafters under metal roofing.

41

Add Bradford R2.5 FIBERTEX™ Rockwool Building Batts between joists.

45

Replace Supa-Ceil plasterboard with 2 layers x 13mm Gyprock Plasterboard CD fixed to metal furring channels (at 600mm max. cts) attached by Gyprock Resilient Mounts

52

Metal roofing with one layer plasterboard fixed to ceiling joists spaced at 600mm cts. plus Bradford Ceiling Insulation between joist. (New Zealand only).

Bradford Acousticon Foil Faced Blanket

Ceiling Joist Gyprock 10mm Supa-Ceil Plasterboard Ceiling

39 – 41

19

Bradford Fibertex Rockwool Batts or (Bradford G lasswool Ceiling Insulation in New Zealand)


A C O U S T I C

D E S I G N

G U I D E

Bradford ACOUSTICON ™ Glasswool Roofing Blanket is faced with THERMOFOIL ™ . ACOUSTICON ™ has been specially developed to provide cost effective rain noise reduction of 18dB(A) insertion loss under metal deck roofing. ACOUSTICON™ has BHP approval for use under all types of Lysaght steel roofing profiles, including Klip-Lok. For more infor mation refer to the Bradford ACOUSTICON™ ‘A Quiet Step Forward’ brochure, available from your nearest Bradford office.

The STC of a roof system (commercial, industrial or domestic) can also be improved with the addition of heavier building materials such as: • addition of insulation between the roof sheeting and Bradford batts above the ceiling, • thicker steel roof sheeting, • using heavier, fire rated plasterboard or multiple layers for the ceiling, • installing a layer of Bradford SOUNDLAGG™ beneath (4 kg/m2 or heavier).

For optimum rain noise reduction under steel roofing in commercial, industrial and residential applications, install 75mm Bradford ACOUSTICON™.

RAIN NOISE REDUCTION WITH METAL DECK ROOFING A common problem of steel roofing is that of rain noise, particularly in tropical climates with high levels of rainfall. Rain falling on metal deck roofing can cause unacceptably high noise levels in the space below the roof. The impact causes the stiff lightweight roof sheeting to vibrate, thus emitting noise. Damping the vibration of the roof sheeting reduces the emitted noise. Rockwool and glasswool blanket products have exceptional noise absorbing properties providing effective damping of the steel roof sheeting. CSR Bradford Insulation in conjunction with CSR Gyprock® have constructed a rain noise testing facility to simulate rain noise using conventional 0.42mm thick BHP Trimdek Hi-Ten metal roof cladding. The rain noise test rig has four nozzles spraying water at high pressure simulate high intensity rainfall. Continuous noise levels of 89dB(A) were created inside the test rig, this noise level was used for controlled testing purposes. Figure 4 shows the rain noise insertion losses achieved by using Bradford Insulation Blankets faced with Thermofoil 729. All tests used 0.42mm BMT BHP Trimdek Hi-Ten steel roofing.

For residential applications, ensure the correct rating of thermal insulation is achieved for roof insulation in your region. At least R2.0 Bradford Rockwool or Glasswool Ceiling Batts should be installed between ceiling joists in conjunction with a Bradford ACOUSTICON™. CSR Bradford Insulation and CSR Gyprock® have conducted many tests using various foil faced roofing insulation blankets, ceiling tiles and fixed plasterboard ceilings. The results of these are shown in Table 5. In tropical climates, roofing insulation is generally installed foil face up, ie. the foil in direct contact with the metal deck roof sheeting. This reduces the insertion loss of the roofing blanket by 2dB. The use of Bradford Rockwool™ ACOUSTICON™ is therefore recommended. Rain noise tests were conducted using the same thickness/density glasswool blanket and varying the surface density of foil. It was found that the mass of the foil has no effect on the rain noise insertion loss achieved by the insulation. ACOUSTICON™ and ANTICON™ roofing blankets should be installed so the blanket is firmly in contact with the steel roofing as shown in Figure 5. This has the added benefit of damping the metal roof sheeting and reducing rain noise.

FIG 4 RAIN NOISE REDUCTION INSERTION LOSSES – FOIL FACED ROOFING BLANKETS.

FIG 5. REDUCTION OF RAIN NOISE – METAL DECK ROOF. 50mm Bradford Rockwool Metal Deck Roofing

Optimum

75mm Bradford ACOUSTICON

50mm Glasswool blanket Bradford Acousticon 50mm Polyester Blanket

10

11

12

13

14

Support Mesh (when specified) 15

16

17

18

19

Bradford Thermofoil Vapour Barrier Purlin

20

Insertion Loss db(A)

20


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D E S I G N

G U I D E

TABLE 5. NOISE REDUCTION CEILING SYSTEMS. Ceiling System Description

Rain Noise Reduction Level dB(A)

• Bradford ANTICON™ R1.5 Blanket hard under metal deck roof

15

• Bradford ACOUSTICON™ hard under metal deck roof

18

• Bradford FIBERTEX™ Rockwool ACOUSTICON™ hard under metal deck roof

19

• Rondo Suspended Concealed Grid Ceiling System. • 1 layer x 13mm Gyprock Plasterboard CD.

22

• Bradford ANTICON™ R1.5 Blanket hard under metal deck roof • Rondo Suspended Exposed Grid Ceiling System. • CSR Gyprock Ecophon™ 20mm Lay-in Ceiling Tiles.

25

• Bradford ANTICON™ R1.5 Blanket hard under the roof. • RONDO Suspended Exposed Grid Ceiling System. • CSR Gyprock CELOTEX™ 16mm Lay-in Ceiling Tiles.

30

• Bradford ANTICON™ R1.5 Blanket hard under the roof. • RONDO Suspended Exposed Grid Ceiling System. • Gyprock 13mm Lay-in Ceiling Tiles.

34

• Bradford ANTICON™ R1.5 Blanket hard under the roof. • RONDO Suspended Concealed Grid Ceiling System. • 1 layer x 13mm Gyprock Plasterboard CD.

37

• • • •

45

Bradford ANTICON™ R1.5 Blanket hard under the roof. RONDO Suspended Concealed Grid Ceiling System. 1 layer x 13mm Gyprock Plasterboard CD. Bradford R1.5 GOLD BATTS or R1.5 Glasswool Building Blanket laid over the ceiling.

• Bradford ANTICON™ R1.5 Blanket hard under the roof. • RONDO Resiliently Mounted Suspended Concealed Grid Ceiling System. 51 • 2 layers x 13mm Gyprock Fyrchek™ Plasterboard. • Bradford R1.5 GOLD BATTS or R1.5 Glasswool Building Blanket laid over the ceiling. Refer to the CSR Gyprock® Fire & Acoustic Design Guide (‘The Red Book’) for additional information on rain noise reduction ceiling systems. See comments regarding: Tropical climate applications in Bradford ACOUSTICON™ brochure. Products for Metal Deck Roofing Systems.

ceiling cavity, the better the low frequency noise reduction.

• Bradford Glasswool Acousticon 75mm. (R1.8) ™

The ceiling can be an important area of a room to place sound absorption particularly, when the remainder of the rooms contains hard reflective surfaces. Rooms having no sound absorbent surfaces typically have high reverberation times. This results in poor acoustics, particularly if communication is required within the room.

• Bradford 50mm Commercial Grade Anticon™. • Bradford Glasswool R1.5 Anticon™ 55mm. • Bradford Glasswool R2.0 Anticon™ 75mm. • Bradford Glasswool R2.5 Anticon™ 95mm. • Bradford 50mm Rockwool ACOUSTICON™.

CEILINGS. Fixed plasterboard ceilings generally provide better sound transmission loss (ie. higher STC) than lightweight suspended ceiling tiles and even plasterboard ceiling tiles. This is because the fixed plasterboard ceiling is better sealed and has less gaps. Multiple layers of plasterboard with resilient mounting and rockwool or glasswool batts in the cavity can provide high STC rating. The larger the

Generally commonly used plasterboard ceilings, whether fixed or lay in ceiling tiles are not very effective at absorbing sound. Typically, sound absorptive ceilings generally consist of: • ceiling tiles made of high density rockwool or glasswool (typically NRC 0.70 – 0.95),

21


A C O U S T I C

D E S I G N

• perforated plasterboard or perforated metal pan ceilings with Bradford Rockwool or Glasswool insulation (faced with a black tissue) above (good sound absorption NRC 0.60 – 0.90),

G U I D E

FIG 6. IMPROVING SOUND TRANSMISSION CONTROL THROUGH CEILING AREA WITH BRADFORD INSULATION. Poor sound privacy caused by sound flanking through lightweight suspended ceiling

• Mineral fibre ceiling tiles (average sound absorption NRC 0.50 – 0.60).

Ducting

Note that better low frequency acoustic absorption results when ceiling tiles are installed with an air cavity. The larger the air cavity, the better the low frequency acoustic absorption.

Ducting

In many commercial office buildings, noises such as conversations, telephones ringing etc can be heard from one office to another (also known as ‘Crosstalk’). This can cause disruption, annoyance, and decreased productivity. Crosstalk usually occurs from sound flanking via the ceiling. In commercial office buildings, the walls are built up to the underside of the lightweight suspended ceilings (usually a metal grid), not to the concrete slab above. The lightweight ceilings tiles used generally have a low STC rating. The void above wall and ceiling allows sound to ‘flank’ from one room to the next via the acoustically weak ceiling tiles. Ideally, the wall should be built up to the underside of the floor above without gaps for sound to pass from one side to the other.

Improved privacy with Bradford Rockwool or Glasswool Ceiling Batts in ceiling space over wall

Ducting

Ducting

To reduce the amount of sound flanking when a wall does not continue to the underside of the floor above, it is recommended that Bradford Rockwool or Glasswool Ceiling Batts be installed between the wall/ceiling and the underside of the floor above. The more compressed the insulation is when installed in this way, the better the acoustic performance. refer to Figure 6.

Bradford Rockwool or Glasswool Ceiling Batts compressed between ceiling and slab above

Alternatively, to reduce flanking via the ceiling, install Bradford Acoustilag™ from the underside of the concrete slab to the ceiling below as shown in Figures 7 and 8. Products - Ceilings. • Bradford Rockwool Ceiling Batts R1.5, R2.0, R2.5, R3.0. • Bradford Glasswool Ceiling Batts R2.0, R2.5, R3.0, R3.5, R4.0. • Bradford Glasswool Ceiling Panel Overlays (optional Black Matt Facing, or ULTRAPHON™) • Bradford Glasswool Absorption Blanket (optional Black Matt Facing or ULTRAPHON™

Ducting

• Bradford Fibertex™ Rockwool (optional Black Matt Facing or ULTRAPHON™)

Cabling

Bradford Rockwool or Glasswool Partition Batts

NOTE: Care must be taken when passing cables through insulation material due to possible overheating. Consult your electrician for more details.

22


A C O U S T I C

D E S I G N

Floor/Ceiling Noise Control Systems.

FIG 7. IMPROVING SOUND TRANSMISSION CONTROL THROUGH CEILING AREA WITH BRADFORD ACOUSTILAG CURTAIN.

Bradford Acoustilag curtain continuous in ceiling area

Multi-storey buildings with hard flooring such as timber, parquetry or tiles etc., can efficiently transmit both airborne and impact noise (structure borne vibration) to the rooms below if appropriate techniques are not incorporated at the time of construction. Installing carpet and underlay on the floor can significantly reduce the impact noise to the room below.

250mm minimum

Installing R2.0 or greater, Bradford Rockwool or Glasswool batts between the floor joists will reduce airborne noise by approximately STC 4 – 6.

C-track or timber batten fixed to soffit 100mm minimum

At the time of printing this guide, The Building Code Of Australia (BCA) ‘Sound Insulation of Floors Between Units’ stated ‘a floor separating sole occupancy units must have an Rw of not less than 45’. (Note: Rw 45 approximately equals STC 45). Floors must also provide insulation against impact generated sound.

Suspended ceiling tiles/plasterboard

FIG 8. JOINTING A BRADFORD ACOUSTILAG CURTAIN.

It should be noted that STC 45 is not always adequate in reducing airborne sound through floors and walls. For better acoustic privacy, it is preferable to use a higher rating of say Rw 50 or preferably Rw 55.

75mm Bradford Reinforced Aluminium Tape

RETRO-FIT OF VIBRATION ISOLATED FLOOR. To reduce impact noise transmission through floor/ceiling systems on existing timber, concrete or tiled floors, a floating floor can be constructed on top of the existing floor. The floating floor should use a resilient damping material. Dense Bradford Rockwool, Glasswool or rubber materials can be used but care is needed to choose a material with the correct stiffness for the application and static load. The services of an acoustic consultant should be engaged to solve floor impact noise problems and for the design of ‘floating floors’. Floating floors should not be mechanical fixed (nailed or screwed) to the existing floor as this will couple the two floors resulting in very little damping. The resilient material should also be used between the edges of the floating floor and the walls of the building. Skirting boards should also be isolated or separated from the floating floor. Note the floor/ceiling and floor/door heights may be affected by the use of a floating floor. Doors may also need undercutting if a floating floor is retro-fitted. Therefore where clearances are important, the floating floor height should be kept to a minimum.

Bradford Acoustilag curtain

50mm min. overlap

PENETRATIONS THROUGH BRADFORD ACOUSTILAG CURTAIN. Cut Bradford Acoustilag curtain to allow installation around pipes, ducting etc.

G U I D E

A tight fit should be maintained to ensure acoustic integrity

23


A C O U S T I C

1.

2. 3.

4.

5.

D E S I G N

G U I D E

REDUCING NOISE TRANSMISSION THROUGH CONCRETE FLOOR/CEILING SYSTEMS. For concrete floor ceiling constructions, use vibration isolated ceiling hangers or resiliently mounted furring channels to support the plasterboard ceiling.

REDUCING NOISE TRANSMISSION THROUGH TIMBER FLOOR/CEILING SYSTEMS. Fit Bradford R2.0 (or greater) Floor Batts, or Rockwool/Glasswool Ceiling Batts tightly between ceiling joists. Fix one layer of 13mm or 16mm Gyprock Fyrchek™ plasterboard to furring channels. For better acoustic performance (to reduce airborne noise), choose a ceiling with more mass ie. multiple layers of Gyprock® plasterboard CD or Gyprock Fyrchek™ plasterboard. CSR Gyprock® Resilient Mounted Furring Channels will further improve acoustic performance as well as impact isolation. To improve impact isolation of floors, use carpet and good quality thick underlay over timber flooring.

Products. • Bradford Floor Batts. • Bradford Glasswool R2.0, R2.5, R3.0, R3.5, R4.0 Ceiling Batts. • Bradford Rockwool R1.5, R2.0, R2.5, R3.0 Wall/Ceiling Batts. • Bradford Glasswool Quietel™ (for impact isolation). FIG 10. TYPICAL METHODS FOR IMPROVING ACOUSTIC PERFORMANCE OF A CONCRETE FLOOR/CEILING SYSTEM. Carpet and underlay

FIG 9. TYPICAL METHODS FOR IMPROVING ACOUSTIC PERFORMANCE OF A TIMBER FLOOR/CEILING SYSTEM.

SYSTEM

Concrete slab floor

STC/Rw

19/20mm Timber Flooring, 200 x 50 Timber Joists at 450mm centres, 1 layer x 13mm Gyprock plasterboard CD.

35

Add Bradford R2.0 GOLD BATTS™ between joists.

39

Add Gyprock Resilient Mounts and Furring Channels at 600mm centres between joists and plasterboard.

52

Add Carpet and Underlay. Add second layer of 13mm Gyprock plasterboard CD

55

Bradford Rockwool or Glasswool Insulation Suspended ceiling system Gyprock resilient mount

Furring channel Higher density Gyprock plasterboard (Soundchek or Fyrchek) and/or multiple layers

Floors. Improved air-borne sound reduction and impact isolation can be achieved by using floating floors as shown in Figures 11, 12 and 13.

Carpet and underlay Timber flooring Bradford Glasswool or Rockwool Insulation

High density, resilient Bradford Rockwool or Glasswool Quietel™ can break the sound and vibration transmission paths while having sufficient compressive strength to support the floating floor and the room contents. Vibrational energy is absorbed in the resilient material rather than transmitted to the building structure. Not only does a floating floor achieve effective structureborne sound control, but it also reduces the air-borne sound transmission to and from the room below.

Timber joists Furring channel Gyprock resilient mount Use higher density Gyprock plasterboard (Soundchek or Fyrchek) and/or multiple layers

A large range of floor/ceiling systems incorporating alternative acoustic upgrades is detailed in Appendix B of this publication.

The Bradford Fibertex™ Rockwool or Glasswool Quietel™ board are laid flat on the floor, ensuring all joints are tightly butted. At the edges of the rooms, the batts continue up the walls. For the concrete floor, waterproof film is then used to cover the batts and a concrete screed floor of suitable thickness is poured.

Refer to the CSR Gyprock® Fire & Acoustic Design Guide ‘The Red Book’ for additional information on floor/ceiling systems. 24


A C O U S T I C

D E S I G N

All equipment is then mounted on the screed floor which is acoustically isolated from the main building structure.

G U I D E

VIBRATION RESISTANCE. As Bradford Fibermesh™ Rockwool is stitched to wire mesh, the blankets are especially resistant to fallout under conditions where vibration is present. Bradford Fibermesh ™ is particularly suitable for applications involving both vibration and high temperature where standard bonded insulation materials are less resistant to the effects of vibration.

FIG 11 TYPICAL FLOATING FLOOR – TIMBER OVER CONCRETE. Particleboard or timber board flooring

Products. • Bradford Glasswool QUIETEL™. Timber battens

• Bradford FIBERTEX™ HD Rockwool. • Bradford FIBERTEX™ HD (High Density) Rockwool.

Plywood Sheeting

• Bradford FIBERMESH™ Rockwool.

Bradford Fibertex Rockwool or Glasswool Quietel

Structural floor

Plumbing.

Air gap at wall

Noisy pipe work is a common problem in many buildings. These days, pipe work building trends commonly use inexpensive, lightweight, easily to install mater ials with thin wall thicknesses which are unacceptably noisy. Offices, hotels, apartments and domestic houses can all benefit from reduced soil and waste pipe noise levels. Designers, hydraulic consultants, engineers, plumbers, owners and occupants of buildings should all take steps to insulate pipes and ducts to reduce noise.

FIG 12 TYPICAL FLOATING FLOOR – CONCRETE OVER CONCRETE.

50mm Concrete

Floor finish

Water flowing through commonly used PVC soil and waste pipes is predominantly high frequency noise. To effectively reduce pipe noise, lag the pipes with Bradford Acoustilag™ 20, 23 or 26 pipe insulation. The 20, 23, and 26 indicate the ‘A-weighted’ [dB(A)] insertion loss achieved by lagging PVC pipes with each of the Bradford Acoustilag™ product respectively. (Refer to Appendix B for additional information).

Wire mesh

Bradford Fibertex Rockwool or Glasswool Quietel

Structural floor

Waterproof film

FIG 13 TYPICAL FLOATING FLOOR – TIMBER OVER TIMBER JOIST CONSTRUCTION. Timber flooring

Note, the 20, 23 and 26dB(A) insertion losses only apply to water flowing through PVC pipes which have been correctly lagged with Acoustilag. Using Acoustilag for lagging other noise sources, eg., a fan casing or sheet metal air ducts, will generally result in lower insertion losses to those quoted, as these noise sources have more low frequency noise energy.

Plywood sheeting Bradford Quietel Board

To achieve the insertion losses quoted, Bradford Acoustilag™ should be installed with all joins of the lagging overlapped or butted, tightly and taped with Bradford 493 reinforced foil tape. Minimising all the gaps increases the acoustic performance of the lagging.

Plywood sheeting Gyprock plasterboard ceiling

Bradford Glasswool/Rockwool Ceiling Batts

NOTE: The upper plywood layer should not be nailed or screw fixed to the timber below. Instead, it should ‘float’ on the base floor to effectively damp vibration. The floor should also be isolated from the walls. CSR Bradford Insulation recommends consulting an acoustic engineer for the design of floating floor systems.

The Building Code of Australia (BCA) states that: ‘Soil and waste pipes are to be separated if a soil or waste pipe, including a pipe that is embedded in or passes through a floor, serves or passes through more than one sole-occupancy unit:

25


A C O U S T I C

D E S I G N

G U I D E

(a) The pipe must be separated from the rooms of any sole-occupancy unit by construction with an STC not less than:

of lightweight plastic pipe to substantially reduce plumbing noise. The heavier, stiffer walls of cast iron pipes effectively reduce noise.

(i) STC 45 if the adjacent room is a habitable room (other than a kitchen); or

• If plastic waste water pipes must be used, use Bradford ACOUSTILAG™ to effectively reduce noise.

(ii) STC 30 if the adjacent room is a kitchen or any other room’.

• Insulate all pipes and plumbing that are chased into brick walls.

The Bradford ‘ACOUSTILAG™ Pipe Insulation’ brochure provides systems using CSR Gyprock ® plasterboard to achieve the STC noise criteria specified by the BCA. The STC 50 system specified in that brochure is intended for applications requiring better acoustic isolation from waste pipe noise than is specified in the BCA eg., board rooms, offices, apartments and hotels etc.

• Select quieter plumbing equipment and appliances eg. cisterns, washing machines, clothes dryers etc. Products. • Bradford ACOUSTILAG™ 20, 23 or 26. • Bradford 493 reinforced foil tape. • ARMAFLEX® insulation.

To achieve the STC’s specified in Table 6, it is imperative that the pipes be correctly lagged (no gaps to allow noise leakage), and the plasterboard ceiling and walls above be airtight with no gaps into the next room.

Quietening Box Gutters & Downpipes.

It is recommended the services of an acoustic consultant or acoustic engineer be used to achieve specified STC ratings. Penetrations, ducting, light fittings, gaps in ceilings etc., can degrade the acoustic rating of the lagging and ceiling system.

Box gutters should be insulated with Bradford FLEXITEL™ or SUPERTEL™ Glasswool (25mm thick) faced with heavy duty foil. Insulation can be attached to gutters using 45mm long Bradford self-adhesive fasteners and washers at 300 mm centres. Insulation should be held firmly against the metal surface for maximum dampening. For better noise reduction, use Bradford ACOUSTILAG™ 20.

To minimise annoyance from plumbing noise, it is advisable, at the design stage, to avoid placing bathrooms and laundries etc., adjacent to noise sensitive areas.

Noisy downpipes should be insulated with Bradford Glasswool Sectional Pipe Insulation faced with Heavy Duty Thermofoil. Alternatively a 25mm wall thickness ARMAFLEX ® pipe insulation or Bradford ACOUSTILAG™ 20 can be fitted around downpipes.

Methods for minimising plumbing noise include: • Select vibration isolated pipe hangers to support pipes and minimise transmission of vibration into the building structure. These will reduce ‘water hammer’ noise when turning the water taps on or off. Alternatively use ARMAFLEX® insulation between pipes and the building structure.

Products. • Bradford Glasswool FLEXITEL™ or SUPERTEL™. • Bradford ACOUSTILAG™ 20.

• Use water supply and drain pipes that are oversized, this may reduce line pressure and minimise flow noise. • Where possible, use cast iron waste water pipes in place

TABLE 6. ACOUSTIC INSULATION SYSTEMS FOR PLUMBING. System STC/Rw Bradford CSR Gyprock® ™ Nº Rating. ACOUSTILAG Plasterboard

Bradford Insulation

BAS 01

30

ACOUSTILAG™ 20

1 layer 10mm Gyprock CD™

Nil

BAS 02

45

ACOUSTILAG™ 20

2 layers 13mm CSR Gyprock CD™

75mm Bradford Glasswool R1.5

BAS 03

45

ACOUSTILAG™ 23



BAS 04

50

ACOUSTILAG™ 23


100mm Bradford Glasswool, R2.0

BAS 05

50

ACOUSTILAG™ 26



Refer to the Bradford ACOUSTILAG™ brochure for additional information. 26


A C O U S T I C

D E S I G N

Insulation Cladding of Pipes, Tanks & Vessels.

G U I D E

FIG 14. BASIC NOISE CONTROL METHODS. Absorbent Lining reduces sound level within enclosure

The insertion loss achieved by cladding pipes, tanks and vessels will depend on a number of factors such as the frequency of the fluid in the pipe the type and mass of the cladding material, the thickness and density of the (rockwool or glasswool) insulation.

Insulation reduces sound flow to outside

Vibration Damping of fan casing reduces sound emission Vibration Isolation Mounting reduces vibration transmission to floor

It should be noted that some of these cladding systems can actually amplify the noise at lower frequencies, particularly if insulation with a high density is used. This generally happens as the tank now has a larger radiating surface. Therefore it is difficult to predict the insertion loss of cladding systems.

REVERBERATION CONTROL. Factories and engineering workshops usually are reverberant spaces due to the lack of sound absorption within the space. Areas with multiple noise sources, such as factories, engineering workshops, bottling plants, machine halls, plant rooms etc usually have a high level of reverberant noise often exceeding the safe regulatory noise level of 85dB(A). The use of sound absorbing materials (such as glasswool and rockwool) to reduce reflected or reverberant sound is the most effective means of reducing overall sound levels in enclosed areas. CSR Bradford Insulation manufacture a range of rockwool and glasswool products with outstanding sound absorption properties. These products have been tested in acoustic reverberation rooms to determine the sound absorption coefficients presented in the technical data section. A range of factory-applied facings is available, the most common being: • black fibreglass tissues (BMF), or ULTRAPHON™ • THERMOFOIL™ laminates (solid and perforated). An extremely effective acoustic absorber for walls and ceilings is Bradford ACOUSTICLAD™ – a roll formed panel, factory lined with Bradford FIBERTEX™ 350 Rockwool. Each panel interlocks with its neighbour forming a structurally reinforced joint. Bradford ACOUSTICLAD™ offers excellent test results with NRC ranges from 0.9 to 1.05. Contact CSR Bradford Insulation for a brochure or refer to Appendix C for the Bradford ACOUSTICLAD ™ absorption coefficients in 1/3 octave bands.

It should be noted that Bradford Rockwool or Glasswool SPI (sectional pipe insulation) will reduce pipe noise but not as effectively as Bradford ACOUSTILAG™ or insulation with a mass barrier. Higher density, means it is less resilient than Bradford ACOUSTILAG™ and more efficiently transfers noise and vibration from the pipe to the cladding/barrier. Note: Bradford ACOUSTILAG™ is not recommended for high temperature applications. Refer to the CSR Bradford Industrial Insulation Design Guide for installation details of cladding and pipe lagging.

Factories & Engineering Workshops. The basic methods by which industrial noise may be controlled are: • Sound absorption – absorbing the noise using mineral fibre materials which can dissipate the sound energy as heat. • Sound insulation (enclosing) – containing the noise in one area so that it does not cause annoyance in other areas. • Vibration damping – damping vibrating surfaces to reduce air borne sound emission. • Vibration isolation – preventing acoustic energy from entering the building structure. These processes are illustrated in Figure 14. As the figure shows, treatment of a factory noise problem often involves a combination of the basic processes.

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G U I D E

TABLE 7. ACOUSTICLAD TEST RESULTS. ™

Acousticlad™ Perforated % Open Area

Test Sample Configuration

15%

50mm thick Bradford FIBERTEX™ 350 Rockwool (60kg/m3) Insulation with black matt facing (BMF) between the Rockwool and Acousticlad face.

1.00

25%

as above

0.95

40%

as above

1.00

15%

23mm thick Mylar film between unfaced Bradford FIBERTEX™ 350 Rockwool and ACOUSTICLAD™ perforated aluminium.

0.90

50mm thick Bradford FIBERTEX™ 350 Rockwool Insulation with black matt tissue between the Rockwool and perforated aluminium. Timber spacers supporting panels with average air gap 30mm.

1.05

15%

Noise Reduction Coefficient NRC Rating

Notes – All acoustic tests were conducted with ACOUSTICLAD™ perforated aluminium panels (0.7mm thick), with Bradford 50mm thick FIBERTEX™ 350 Rockwool (60kg/m3) insulation. – Acoustic tests were conducted in the reverberation room at the National Acoustic Laboratories, Chatswood, Sydney, Australia. – See Appendix C for absorption coefficients at each 1/3 Octave band frequency.

A commonly used cost effective method for fixing insulation (generally faced with perforated foil) on walls and ceilings uses drive pins and speed clips. These eliminate the need for battens or furring channels. The drive pins are fixed to the wall usually at 450mm centres. The insulation is pushed through the pins and held onto the pin by the speed clips of a suitable size.

Bradford ACOUSTICLAD™ perforated metal is available with percentages of open area ranging from 10% to 55% and in a number of finishes including: • galvanised steel, • powder coated steel, • stainless steel and • aluminium.

Rigid facings such as perforated metal or pegboard are unsuitable for this application method. The advice of adhesive suppliers should be sought before using adhesively fixed pins in lieu of drive pins.

Fixing details for Bradford ACOUSTICLAD™ are available from your nearest Bradford office. Bradford Rockwool and Glasswool insulation is available with a range of facings, including:

Ceilings may be lined by the same methods as walls. An alternative approach is to use a fully exposed metal suspension grid which makes it a simple matter to achieve any air gap required behind the batts

• perforated metal or expanded metal. • perforated foils, • pegboard,

Factories contain noise which predominantly has most energy at low frequencies which is difficult to absorb unless very thick insulation is used. To increase the low frequency sound absorption of perforated noise absorbers (such as Bradford ACOUSTICLAD™), introduce an air gap behind the insulation. This can be achieved by using larger battens or furring channels with chicken wire to retain the batts in position, as shown in Figure 15 below. Better acoustic absorption results when the depth of the air cavity is at least as thick as the insulation.

• wire, • plastic mesh. Any perforated sheet facing should have an open area greater than 10% to maximise acoustic absorption. Other common methods for acoustic wall treatment involve: • fixing timber battens or steel furring channels or ‘Z’ sections at a spacing to suit the facing sheets. Bradford Rockwool and Glasswool batts are cut to size if necessary and friction fitted between the supports. The protective facing (e.g. perforated or expanded metal, plastic mesh, pegboard, wire etc.) is fixed to the furring sections or battens by nails, screws, or rivets as appropriate. Cover strips are used to improve the appearance.

Alternatively, rockwool or glasswool insulation greater than 75mm can be used with acoustically transparent facings mentioned above.

28


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FIG 15. ABSORPTIVE LINING WITH AIR GAP TO BOOST LOW FREQUENCY ABSORPTION (PLAN VIEW). Chicken wire

Bradford Fibertex Batts

Structual wall

G U I D E

FIG 16. BRADFORD ‘ACOUSTIC BAFFLES’ USED TO ABSORB SOUND FROM NOISY EQUIPMENT.

Air gap

Battens

Facing eg. perforated metal

Products. • ACOUSTICLAD™ with perforated metal facing is available in various thicknesses and open area percentage to accommodate acoustic absorption requirements. The following Bradford products can also be used: • Bradford Rockwool FIBERTEX™ 350, 450.

Installation Method 1.

• Bradford Glasswool FLEXITEL , SUPERTEL , ULTRATEL™ with perforated metal, expanded metal, wire, meshes or perforated heavy duty grade foil facings. ™

™

The baffles can be individually suspended from the roof structure using ‘S’ hooks, galvanised wire or fine chain. In this case, suspend baffles approximately 1 metre below the ceiling level if possible.

Bradford Acoustic Baffles.

FIG 17. ACOUSTIC BAFFLES SUSPENDED AND ARRANGED IN A CROSS-HATCH PATTERN.

Large factories or buildings may need a greater area of acoustic absorbing insulation than just the wall area, or may need it concentrated in a particularly noisy section of the building.

Roof framing

Bradford Rockwool Acoustic Baffles may be suspended in any desired pattern to achieve extra sound absorption in a building. Refer to Figure 16 and 17.

Suspension wire or chain

'S' Hook

Sound absorption coefficients of Bradford Rockwool Acoustic Baffles are shown in Table 8.

BAFFLE INSTALLATION. Two popular methods of installation are detailed. Baffles may be installed at any height, and do not need to be all in the same plane. A regular pattern such as parallel rows or a staggered, cross-hatched pattern is most easily installed using a suspended ceiling grid. Determine the number of acoustic baffles to be installed to meet the noise reduction required. The typical number of baffles is 1 baffle per square metre of ceiling area. Allowance should be made for lights and sprinklers.

Bradford Acoustic Baffles in cross-hatch pattern

TABLE 8. SOUND ABSORPTION COEFFICIENTS OF BRADFORD ACOUSTIC BAFFLES. Product

Density Thickness Facing (kg/m3) (mm) 125 Bradford Acoustic Baffle 60 50 30µm 0.18 plastic film 29

250 0.44

Frequency (Hz) 500 1000 2000 4000 5000 0.83 1.25 1.14 0.96 0.94

NRC 0.90


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G U I D E

noise level by about 5dB more than a 1mm sheet steel enclosure, assuming all other conditions are equal.

Installation Method 2. Inverted 50mm x 12mm aluminium U-channels are fixed to the underside of a ceiling grid. The baffles are then secured to the U-channel using self tapping screws.

Enclosures do not attenuate all frequencies of sound equally, so the transmission loss achieved will depend on the frequency spectrum of the noise source. High frequency noise is more easily attenuated than low frequency noise.

FIG 18. ACOUSTIC BAFFLES FIXED IN ALUMINIUM TRACK AND ARRANGED IN A PARALLEL PATTERN.

Thus, while a lightweight enclosure may provide effective transmission loss for a high frequency noise source, it could however be inadequate for low frequency noise sources.

Main suspension grid

Flanking transmission paths permit sound to by-pass the acoustic enclosure. Typical examples are air gaps, windows, doors, service penetrations etc. To avoid severe reductions in insulation performance, steps should be taken to eliminate these flanking paths as far as practical. Caulking of air gaps and penetrations, use of door seals or even double doors, resiliently mounted double glazing, use of flexible couplings on pipes and ducting which penetrate the enclosure are all means of reducing flanking transmission.

Aluminium channel

Bradford Acoustic Baffles arranged in parallel pattern

Products.

Flanking through the floor of an enclosure can limit the transmission loss. Sound and vibration entering the floor on the noisy side of the enclosure can be re-radiated to some extent on the other side.

• Bradford Rockwool Acoustic Baffles.

Acoustic Enclosures.

The sound insulation performance of lightweight enclosures may be significantly improved by the use of double-leaf construction with a core of sound absorbing rockwool or glasswool as shown in Figure 20. The performance will be further enhanced if the two leaves are of different surface densities eg: one leaf may be 1.6mm steel sheet while the other is 1.2mm steel sheet. This reduces resonant coupling between the sheets.

Enclosures are an effective method of reducing noise emitted from a particular machine or noise source. They should be constructed of solid materials such as bricks, sheet steel, timber, plasterboard etc. Enclosures reduce noise more effectively when they are airtight, with no gaps or openings. This is not always possible as the machinery inside may need to be accessed by other machines or people, or require air flow for cooling.

The sound reduction achieved depends on the surface density of the enclosure. Heavy materials like steel sheet greater than 1.0mm, 16mm plywood or 19mm particle board are typically used.

Enclosures built around machiner y actually concentrate the noise inside the enclosure. Therefore it is good practice to line the inside of enclosures with Bradford Rockwool or Glasswool to reduce reverberant noise levels inside.

As well as trapping sound, enclosures of the type shown in Figure 19 and 20 will also trap heat. It is often necessary therefore to ventilate these enclosures to avoid overheating of the enclosed machinery. Ventilation openings must also be acoustically treated to reduce the escape of sound through these openings. The use of packaged attenuators, insulation lined ducts or acoustic louvres are commonly used.

A simple acoustic enclosure is shown in Figure 19. It has three main components: (i) an internal lining of sound absorbent rockwool or glasswool insulation to reduce the noise level inside the enclosure. (ii) a heavy barrier to reduce sound transmission to the outside.

Absorptive treatment may include not only lining the walls and ceiling of an enclosure but also the use of discrete screens or baffles. The latter are of particular value where it is important that the absorptive treatment does not interfere with the dissipation of heat. Where heat could cause a problem, then Bradford Rockwool Acoustic Baffles are specially designed for suspension below existing

(iii) a resilient pad of felt or rubber to isolate the enclosure from the floor (optional). Broadly speaking, the sound transmission loss of an enclosure improves by about 5dB for every doubling of the surface density (mass per square metre or kg/m2). Thus, a 2mm thick sheet steel enclosure will reduce the 30


A C O U S T I C

D E S I G N

factory roofs. Their sound absorption performance is detailed in the previous section. Baffles will not however be as effective at reducing noise as an enclosure.

FIG 19. ACOUSTIC ENCLOSURE. Bradford Fibertex 450 Rockwool or Ultratel

G U I D E

Heavy Gauge Steel Sheet

An example of an acoustic enclosure for very high acoustic insulation is detailed in Fig 21. It shows a room within a room. These rooms are vibration isolated from each other.

INSTALLATION DETAILS. Installation of the sound absorbing rockwool or glasswool batts to the inside surfaces of the enclosure proceeds in a similar manner to that previously described for reverberation control. Where double-leaf construction is employed a larger number of variations are possible. One simple yet effective procedure follows: Construct a suitable frame using steel angles, channels, or box sections to provide at least 63mm clearance between the two leaves. (Note the wider the cavity, the better the low frequency sound transmission loss). Mount this frame on a continuous thick rubber mat. The outer steel sheeting should then be fixed to the frame as shown in Figure 21, using rubber strips to reduce sound transmission from the frame to the sheet.

Rubber Mounting

FIG 20. ACOUSTIC ENCLOSURE WITH DOUBLE-LEAF CONSTRUCTION. Bradford Fibertex 450 Rockwool or Ultratel

Heavy Gauge Steel Sheet

Rubber Mounting

FIG 21. ACOUSTIC ENCLOSURE WITH VERY HIGH ACOUSTIC INSULATION. Heavy duty flexible pipe connection, and resilient mounted pipe/ductwork

Minimum cavity of 200mm

Bradford Insulation Blanket Two steel soundproof doors with all edges sealed

Existing window

Small double glazed viewing window

Bradford Insulation Blanket in cavity

Main structure of building Resilient/floating floor system

31


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D E S I G N

Fix 50mm thick FIBERTEX R350 to the inside of the sheeting using weld pins and speed clips. Bend over the ends of the pins if necessary to avoid contact with the inner steel sheeting when installed.

G U I D E FIG 22. A PARTIAL ENCLOSURE.

™

The inner sheeting may now be fixed to the frame, again as shown in Figure 21. The sound absorbing rockwool or glasswool batts may now be fixed to the inside of the inner sheet using weld pins, speed clips, and a suitable facing (wire, meshing, perforated foil). Alternatively, a perforated metal (such as Bradford ACOUSTICLAD™) or expanded metal can be used, or for an aesthetically pleasing finish. Any gaps, openings or joins in the outer leaf of the enclosure, should be caulked and doors should use acoustic door seals. Products. • Bradford Rockwool FIBERTEX™ 350, 450. • Bradford Glasswool FLEXITEL™, SUPERTEL™, ULTRATEL™. • Bradford ULTRAPHON™ facing. FIG 23. TYPICAL NOISE PROBLEM WITHOUT ACOUSTIC ENCLOSURE .

Partial Enclosures & Screens. It is not always practical to totally enclose a noisy machine. However, the use of a partial enclosure or screening will still achieve some reduction in noise levels particularly close to the screens. The previous discussion on total enclosures also applies to partial enclosures. However the overall noise reduction of partial enclosures will not be as great, due to the openings. As far as is practical, employee work stations should be located in the shadow zone of the screening and not in line with the openings in the enclosure. Reflective surfaces near openings in a partial enclosure should be treated with rockwool or glasswool insulation to absorb noise.

FIG 24. IMPROVED NOISE CONTROL WITH A PARTIAL ENCLOSURE.

Where a particular noise source contr ibutes significantly to the overall noise level in a room, it may be controlled by a partial enclosure of the type shown in Figure 22. Much of the sound produced within the enclosure is absorbed, thus reducing the amount of sound radiated into the room. Partial enclosures can be simply fabricated by sandwiching FIBERTEX™ Rockwool or Glasswool Batts between an outer sheet of plywood and an inner lining of pegboard. Alternatively, plain hardboard, particleboard, plasterboard, or sheet metal may be used for the outer sheet, while the inner lining may be perforated or expanded metal. The effectiveness of a partial enclosure depends in part on the weight of the outer sheet and the percentage of the machinery that is enclosed. 32


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G U I D E

The choice of which type of Bradford FIBERTEX Rockwool or Glasswool to use should be based on the frequency spectrum of the noise source. Select the material with the highest sound absorption for the dominant frequency bands of the noise source. High frequency sound absorption will be affected by the inner lining. Should the dominant frequency bands of the noise source be above 1000 Hz, the inner lining should have a perforated open area of 11% or more to ensure optimum sound absorption.

concerned. However, local absorption permits reduction in sound levels without significantly altering the room reverberation time.

The effect of local absorption will be limited by the need to provide access or ventilation to the equipment

• Bradford Glasswool FLEXITEL™, SUPERTEL™, ULTRATEL™.

™

Figures 23 and 24 show a typical application of a partial enclosure to reduce noise reaching an operator. Figure 23 and 24 illustrate the use of partial acoustic enclosures in a car assembly line application. Products. • Bradford Rockwool FIBERTEX™ 350, 450.

• Bradford ULTRAPHON™ or HD Perf. facings. FIG 25. TYPICAL NOISE PROBLEM WITHOUT ACOUSTIC ENCLOSURE.

FIG 26. TYPICAL PARTIAL ACOUSTIC ENCLOSURE APPLICATION.

33


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G U I D E

Vibration Damping.

ACOUSTIC SCREENS. Simple acoustic screens may be fabricated as shown in Figure 27, and these may be supported in any framing suitable to the particular application. Screens can act in three ways: • As local sound absorbers (i.e. a simple partial enclosure), • As reverberation control (i.e. more absorption is introduced to the room), • As a partial barrier (i.e. an acoustic shadow zone is created behind the screen). For maximum effect, acoustic screens should be located as close as practical to the noise source or to people affected by the noise. They should be as large as possible, at least the height or width of the machine or noise source. Air flow requirements should be considered.

Vibrating surfaces such as fan casings, pipes, and ducting can be a major source of noise. Lagging these surfaces will significantly reduce the noise radiated from the sources. When treating such surfaces in this manner, it is essential that lagging be applied over the entire sound-radiating surface. It is also necessary to avoid bridging connections between the radiating surface and the outer cladding. Otherwise, the vibration will be transmitted directly to the cladding which will itself become a sound-radiating surface. FIG 28. FIXING STEEL SHEET TO MINIMISE NOISE TRANSMISSION.

Products. • Bradford Rockwool FIBERTEX™ 350, 450. Enclosure Frame

• Bradford Glasswool SUPERTEL™, ULTRATEL™.

Other steel Sheet

• Bradford ULTRAPHON™ facing. FIG 27. A SIMPLE ACOUSTIC SCREEN.

Fixing Screw

Decorative, non-reflective fabric

Rubber Grommet

VIBRATION ISOLATION. Vibration isolation involves the isolation of vibrating machinery from the building structure. In practice this is achieved by using flexible, resilient mountings, such as rubber-in-shear rubber or steel springs. Where equipment is mounted on inertia blocks, there are often advantages in using a continuous layer of dense rockwool or rubber as the vibration isolator.

Heavyweight plywood or metal core

Fibertex Rockwool or Glasswool Protective metal edges

FIG 29. FIBERTEX™ ROCKWOOL AS A VIBRATION ISOLATOR.

NOTE: Where the noise level emitted by a factory is above acceptable community standards, it is wise to engage the services of a noise control engineer. Environmental noise legislation is quite complex, and failure to comply with the relevant noise criteria may result in severe penalties. Each situation presents its own unique problems which must be identified and then corrected.

Resilient Fibertex Rockwool HD Inertia Block Z-Section Waterproof Film

Plant Room Floor

34


A C O U S T I C

D E S I G N

By acting equally under the entire area of the block, the layer of rockwool dampens the rocking motion that may be present and eliminates point loading on the structural floor. The static deflection characteristics of CSR Bradford Insulation products are shown in Product Guides.

G U I D E

FIG 31. TYPICAL APPLICATIONS OF ARMAFLEX® (a) PIPE SUPPORT.

The use of rockwool as an isolator is not recommended where the required static deflection exceeds 10mm. In such cases it is advisable to use rubber or steel springs.

VIBRATION RESISTANCE. Bradford FIBERMESH™ is particularly suitable for applications involving both vibration isolation as well as high temperature, where standard bonded insulation materials are less resistant to the effects of vibration. Bradford FIBERMESH™ rockwool is stitched to wire mesh making the blankets especially resistant to fallout under conditions where vibration is present.

FIG 32. TYPICAL APPLICATIONS OF ARMAFLEX® (b) PENETRATION THROUGH SOUND INSULATING WALL.

FIG 30. DENSE GLASSWOOL BOARD USED FOR VIBRATION ISOLATION OF MACHINES. Sound Insulating Wall

Use vibration absorbing flexible couplings on all rigid connections to the vibration source

False flange (must not contact pipe)

Pipe

Bradford Armaflex Flexible Pipe Insulation

Flexible Mastic (sealing gap between flange and pipe)

INSTALLATION RECOMMENDATIONS. Installation commences with the laying of a suitable water proof film on the plant room floor. The FIBERTEX™ Rockwool batts are laid flat on the film, ensuring all joints are tightly butted. The area covered by the batts should exceed the dimensions of the inertia block by at least 50mm on each side. The waterproof film should be wrapped around the outer edges of the FIBERTEX™ Rockwool batts and retained in position by metal U-channels, timber battens, or other suitable protective treatment. The edging material, when installed, must allow for a 3mm gap between itself and the inertia block. This gap, and any gaps or joins in the edging material should be sealed with a flexible, waterproof mastic.

Bradford Quietel Glasswool Board for vibration isolation

Isolation of machinery from the floor structure will not achieve its design performance if flanking vibration paths remain. All connections to the equipment, such as piping, ductwork, and electrical conduits, should incorporate a vibration absorbing flexible coupling, and should also be isolated from the building structure by flexible mounts. ARMAFLEX® flexible pipe insulation, a closed cell nitrite rubber tubing, provides an excellent vibration isolation gasket for piping and conduit. Typical applications are shown in Figures 31 and 32.

35


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G U I D E

based on the selected Noise Rating number plus corrections for the characteristics of the room and the distance to the nearest occupant. If the design goals have not been achieved, the additional attenuation needed at each frequency band must be designed into the system. Duct attenuators can be used, however the most economical approach where space permits is using internal duct liners.

Air Conditioning Noise Control. Noise arises in air handling systems principally from fans and from air flow generated noise in both ducts and through registers. It is sometimes necessary to deal with sound transmitted along a duct from one room to another. This section provides methods and data to assist in the design of internal duct lining to control noise.

FAN NOISE. Generally the fan manufacturer will provide data on fan noise characteristics. However if no data is available, the following empirical formulae developed by Beranek may prove useful: SWL = 77 + 10 log kW + 10 log P SWL = 25 + 10 log Q + 20 log P SWL = 130 + 20 log kW - 10 log Q Where: SWL = overall fan sound power level, dB kW = rated motor power, kW P = static pressure developed by fan, mm w.g. Q= volume flow delivered, m3/h Octave band sound power levels are then found by subtracting correction factors from the overall sound power level calculated by any one of the above formulae. Maximum noise usually occurs from the blade tip frequency of the fan. This is determined from the number of blades on the fan rotor multiplied by the number of revolutions per second. The octave band in which the blade tip frequency falls will have the highest sound power level and therefore the smallest correction factor to be subtracted from the overall sound power level. A fan’s rotating blades produce tones at the blade pass frequency (BPF).

The fan in air conditioning systems is generally the main noise source. The types of fans used are either axial type or centrifugal type fans. Axial fans generate a higher proportion of high frequency noise but less low frequency noise than centrifugal fans of similar duty. The fan manufacturer should be able to supply sound power spectrums of fan noise. Noise also arises from airflow generated in both the ducts and registers (also known as regenerated noise). Usually the greater the velocity of the air through the ducts, the higher the regenerated noise level.

NOISE CRITERIA. Noise Criteria curves (NC) and Noise Rating numbers (NR) have been developed to approximate loudness contours and speech interference levels at particular frequencies. These criteria graphs indicate a sound pressure level at each frequency that will be appropriate in a particular environment. Noise Rating numbers are covered by Australian Standard AS1469 : 1983 ‘Acoustics – Methods For The Determination Of Noise Rating Numbers’. Sound levels are often expressed in A-weighted decibels. Australian Standard AS2107 : 1987 ‘Acoustics – Recommended Design Sound Levels And Reverberation Times For Building Interiors’ covers the recommended background sound levels for occupied spaces makes use of the dB(A) weighting. It is recommended that design calculations of noise reduction use Noise Rating numbers and then convert to dB(A) at the end of the calculations.

BPF =

rpm x 60 N

Where: BPF = blade pass frequency (Hz)

GENERAL PROCEDURE. The fan sound power level is first established, then each duct path is examined separately. Noise generated by 90° elbows and branches is estimated using data from the Sound and Vibration section of the ASHRAE Guide and Data Book and added to the fan noise. From this is deducted any branch take-off losses and the natural attenuation due to straight runs of duct work, elbows and end reflections losses, again using the data tabulated in the ASHRAE Guide. The resultant sound power level represents the noise reaching the conditioned space. This is compared to the design requirements for the space

rpm = revolutions per minute N = number of fan blades Har monics and sub-har monics may result at frequencies which are multiples of the blade pass frequencies. The recommended correction factors are indicated in Table 9.

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TABLE 9. CORRECTIONS FOR FAN SOUND POWER LEVELS. Blade Tip Frequency Fan Type Centrifugal Backward Curved Blades Forward Curved Blades Radial Blades Axial Mixed Flow

Band 4 2 3 7 0

1st Octave 6 6 5 9 3

DUCT ATTENUATION. Air handling duct work is internally lined using rockwool or glasswool insulation boards or blankets faced with an acoustically transparent facing to provide adequate sound absorption by the insulation. In addition the facing must provide minimal airflow resistance inside the duct and may also need to act as a vapour barrier. For maximum sound absorption, the duct liner’s facing should be as light and porous as possible to allow sound to penetrate it. Internal duct liners commonly use Bradford R-rated Ductliners, SUPERTEL™ or ULTRATEL™ Glasswool faced with: • Bradford ACOUSTITUFF™ • Bradford ULTRAPHON™ woven glass fabric, • Lightweight THERMOTUFF™ , • Heavy Duty 750P THERMOFOIL™ perforated, • Black or clear fibreglass tissue or • Fine, lightweight polyester films (Mylar or Melinex). Appendix C, Table C7, Contains comparative noise reduction coefficients for Bradford products.

2nd Octave 9 13 11 7 6

3rd Octave 11 18 12 7 6

4th Octave 13 19 15 8 10

5th Octave 16 22 20 11 15

6th Octave 19 25 23 16 21

The most important octave bands where fan noise is concerned are the 125Hz and 250Hz bands. Ducts internally lined with a suitable length and at least 50mm thickness of Bradford Glasswool or FIBERTEX ™ Ductliner can effectively reduce the low frequency component of fan noise. The thicker the internal duct liner, the better the low frequency sound absorption. The thermal performance of the insulation for air conditioning ducts can be calculated using the data in the CSR Bradford Insulation Air Conditioning Design Guide. Table 10 is a guide to the attenuation achieved by lining two opposite sides of a duct with Bradford Glasswool ULTRATEL™ at 50mm and 100mm thickness. The distance ‘D’ is the depth in mm between the linings. It is assumed that any facing material used is deemed acoustically transparent. If the duct is to be lined on all four sides, the total attenuation may be obtained by arithmetically adding the attenuation achieved by lining the other two opposite sides.

TABLE 10. CALCULATED LINED DUCT ATTENUATION, dB/m. Lining Thickness 50mm

Depth Between Linings ‘D’ mm 200 300 400 600 800 1000 100mm 200 300 400 600 800 1000 Limit of Attenuation

125 1.3 1.2 1.2 1.0 0.6 0.5 4.3 3.2 2.1 1.7 1.3 0.8 26

250 4.5 3.3 2.6 1.5 1.2 1.1 8.8 6.5 5.4 3.8 2.9 2.0 31

Frequency (Hz) 500 1000 10.8 15.8 7.7 9.2 5.8 8.0 3.5 3.4 2.4 2.0 2.0 1.1 14.5 15.8 10.2 9 7.9 8.0 5.2 3.4 4.0 2.0 3.1 1.1 38 42

2000 15.4 6.8 3.8 1.6 1.0 0.6 15.4 6.8 3.8 1.6 1.0 0.6 50

4000 7.7 3.4 1.9 0.9 0.4 0.3 7.7 3.4 1.9 0.9 0.4 0.3 60

Table 10, shows that the smaller the duct dimensions, the higher the attenuation per length of duct. 1 Sound Research Laboratories, Noise Control in Building Services, Pergamon Press, First Edition 1988.

37


A C O U S T I C Straight Duct Circular/Oval or Rigid Walled (unlined)

x

Straight Duct Rectangular (unlined) x

x

D E S I G N

G U I D E

TABLE 11. ATTENUATION OF UNLINED DUCTS. Duct Dimensions Octave Band Centre Frequency Hz) ‘x’ (mm) 63 125 250 500 1k 2k Attenuation dB/metre run 0.07 0.10 0.10 0.16 0.33 0.33 75 – 200 0.07 0.10 0.10 0.16 0.23 0.23 200 – 400 0.07 0.07 0.07 0.10 0.16 0.16 400 – 800 0.03 0.03 0.03 0.07 0.07 0.07 800 – 1500 Duct Dimensions ‘x’ (mm)

63

75 – 200 200 – 400 400 – 800 800 – 1500

0.16 0.49 0.82 0.66

Octave Band Centre Frequency Hz) 125 250 500 1k 2k Attenuation dB/metre run 0.33 0.49 0.33 0.33 0.33 .66 0.49 0.33 0.23 0.23 0.66 0.33 0.16 0.16 0.16 0.33 0.16 0.10 0.07 0.07

4k 0.33 0.23 0.16 0.07 4k 0.33 0.23 0.16 0.07

TABLE 12. IN-DUCT ATTENUATION WITHIN EXTERNALLY LAGGED DUCTS. Straight Duct Duct Dimensions Octave Band Centre Frequency Hz) Circular/Oval or ‘x’ (mm) 63 125 250 500 1k 2k 4k (externally lagged) Attenuation dB/metre run 0.14 0.20 0.20 0.32 0.33 0.33 0.33 75 – 200 x 0.14 0.20 0.20 0.32 0.23 0.23 0.23 200 – 400 0.14 0.14 0.14 0.20 0.16 0.16 0.16 400 – 800 0.06 0.06 0.06 0.14 0.07 0.07 0.07 800 – 1500 Straight Duct Rectangular (externally lagged) x

x

Duct Dimensions ‘x’ (mm)

63

75 – 200 200 – 400 400 – 800 800 – 1500

0.33 1.00 1.64 1.32

Octave Band Centre Frequency Hz) 125 250 500 1k 2k Attenuation dB/metre run 0.66 1.00 0.66 0.33 0.33 1.32 1.00 0.66 0.23 0.23 1.32 0.66 0.32 0.16 0.16 0.66 0.32 0.20 0.07 0.07

4k 0.33 0.23 0.16 0.07

TABLE 13. ATTENUATION OF RADIUS BENDS. Straight Duct Circular/Oval or Rigid Walled (unlined) D

D

Duct Dimensions ‘D’ (mm)

63

150 – 250 250 – 500 500 – 1000 1000 – 2000

-

Octave Band Centre Frequency Hz) 125 250 500 1k 2k Attenuation dB 1 2 1 2 3 1 2 3 3 1 2 3 3 3

4k 3 3 3 3

There are positive steps that can be taken to counter the effect of flanking transmission but for the purpose of this guide it is recommended that, in using these Tables, reliance should not be placed on achieving attenuation in excess of the limiting values shown. If attenuation beyond these limits is required, it should be achieved by other acoustic treatment or lining at a location remote from the length of duct under consideration.

For more examples of duct losses, refer to ASHRAE (American Society Of Heating Refrigeration Engineers) publications. It should be noted, that a limit to the attenuation of sound in duct work may be imposed by flanking transmission or noise breakout. This particularly occurs when the aim is to achieve high attenuation in a short length of straight duct. 38


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G U I D E

TABLE 14. ATTENUATION OF MITRE (90°) BENDS. Mitre Bend (unlined)

D

Mitre Bend (lined) D Lining Thickness = 10 Lining to extend distance 2D or greater

D

Duct Dimension ‘D’ (mm)

63

75 – 200 100 – 150 150 – 200 200 – 250 250 – 300 300 – 400 400 – 500 500 – 600 600 – 700 700 – 800 800 – 900 900 – 1000 1000 – 1100 1100 – 1200 1200 – 1300 1300 – 1400 1400 – 1500 1500 – 1600 1600 – 1800 1800 – 2000

1 1 1 2 2 3 5 6

Duct Dimension ‘D’ (mm)

63

75 – 200 100 – 150 150 – 200 200 – 250 250 – 300 300 – 400 400 – 500 500 – 600 600 – 700 700 – 800 800 – 900 900 – 1000 1000 – 1100 1100 – 1200 1200 – 1300 1300 – 1400 1400 – 1500 1500 – 1600 1600 – 1800 1800 – 2000

1 1 1 2 2 3 4 5

39

Octave Band Centre Frequency Hz) 125 250 500 1k 2k Attenuation dB 1 7 5 8 1 7 7 5 8 4 1 7 7 4 2 8 5 3 5 8 4 3 6 8 4 3 1 7 7 4 3 2 8 5 3 3 3 8 5 3 3 5 8 4 3 3 6 8 4 3 3 7 7 4 3 3 7 7 4 3 3 8 7 3 3 3 8 6 3 3 3 8 5 3 3 3 8 4 3 3 3 8 4 3 3 3

Octave Band Centre Frequency Hz) 125 250 500 1k 2k Attenuation dB 2 13 1 7 16 4 13 18 1 7 16 18 2 11 18 18 4 14 18 18 1 5 16 18 16 1 8 17 18 16 2 13 18 18 17 3 14 18 17 16 4 15 18 18 17 5 16 18 17 17 7 17 18 16 17 8 17 18 16 17 10 17 18 16 18 11 18 18 16 18 12 18 18 16 18 14 18 18 17 18 15 18 18 17 18 16 18 17 17 18

4k 7 4 4 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3

4k 18 18 18 16 17 17 17 17 18 18 18 18 18 18 18 18 18 18 18 18


A C O U S T I C

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MEASURED SOUND ATTENUATION IN DUCTS. CSR Bradford Insulation has carried out extensive research to establish the real performance of duct liners in reducing noise levels. Tests have been carried out on Bradford Insulation 25mm and 50mm duct liners using different duct sizes and lengths of lined duct. Figures 33, 34 and 35 have been plotted from measurements of sound levels taken in standard sheetmetal ducts using 25mm duct liners. The graphs present a conservative guide to the performance of all Bradford Glasswool and Fibertex™ Rockwool duct liners at 25mm thickness. Four different lengths of lining are shown for each of three duct sizes.

G U I D E

FIG 34. SOUND ATTENUATION IN DUCT SIZE 406 x 813mm. 60

Insertion Loss (dB)

50

40

30

20

Bend

4.9m 3.7m 2.4m 1.2m

10

0

63

125

250

500

1000

2000

4000

Frequency (Hz)

FIG 35. SOUND ATTENUATION IN DUCT SIZE 508 x 610mm.

60

60

50

50

40

40

4.9m

30

3.7m 2.4m

20

63

125

250

500

1000

2000

30

20 Bend

Bend 1.2m

10

0

Insertion Loss (dB)

Insertion Loss (dB)

FIG 33. SOUND ATTENUATION IN DUCT SIZE 254 x 305mm.

4.9m 3.7m 2.4m 1.2m

10

0

4000

Frequency (Hz)

63

125

250

500

1000

2000

4000

Frequency (Hz)

TABLE 15. INSERTION LOSS CHARACTERISTICS OF FACED DUCTLINERS. (INTERNAL DUCT LINING) Insertion Loss (dB loss 600x600x4000 test duct) Product Facing Thickness Octave Band Centre Frequency (Hz) mm 63 125 250 500 1000 2000 4000 Bradford Glasswool BMF 50 1.4 4.6 16.8 53.2 51.6 32.4 24.4 ™ DUCTLINER THERMOFOIL 50 1.6 5.3 18.9 53.4 48.3 31.8 24.6 32 kg/m3 HD Perf. 23µm Melinex + THERMOFOIL™ 50 1.9 5.7 21.1 26.6 16.7 12.9 12.8 HD Perf. ACOUSTITUFF™ 50 2.5 4.7 21.3 46.8 39.3 23.3 17.4 ™ ULTRAPHON 50 2.0 5.0 20.9 51.5 46.6 30.3 27.5 Bradford Premium Ductliner ULTRATEL ACOUSTITUFF™ 50 – 4.9 14.2 39.0 37.0 22.4 18.6 48 kg/m3 Bradford FIBERTEX™ THERMOFOIL™ DUCTLINER HD Perf. 50 2.8 5.8 19.9 56.6 49.1 32.4 24.6 3 60 kg/m 40


A C O U S T I C

D E S I G N

Research has also been carr ied out on sound attenuation characteristics of different facing materials used on duct liners. Insertion Loss measurements carried out in accordance with Australian Standard AS1277 : 1983 ‘Acoustics - Measurement Procedure For Ducted Silences’ demonstrate the effect of typical facing materials on the acoustic performance of Bradford Glasswool and FIBERTEX™ duct liners, as shown in Table 15.

G U I D E

Constraints accuracy = ± 10% frequency range, 250 to 2000Hz α ≤ 0.8 for circular ducts, Diameter > 0.15m for rectangular ducts, width or height ≤ 900mm and width <2 0.5 < height

An alternative rough indication of attenuation achieved by the lining of ductwork can be found by use of the ‘Sabine’ formula. This gives reasonable results for straight ducts at low frequencies provided the smallest duct dimension is within the range 150 mm to 450 mm and the width is no greater than three times the depth. 1.07 Pα1.4 Attenuation (dB/m) = A

The location of duct lining can be a critical factor. It is normally placed at the start of a duct system to attenuate fan noise and near the outlets to correct air flow generated noise from dampers and fittings, and to restrict noise transmission from adjacent areas through the air conditioning duct.

Where:

a

D

P = inside perimeter of lined duct, m A = internal cross-sectional area, m2 α = absorption coefficient of the duct liner at the frequency concerned.

b

TABLE 16. SOUND ABSORPTION OF BULK INSULATION DUCTLINERS . Product

Facings

Bradford Glasswool DUCTLINER/ SUPERTEL™ 32kg/m3

THERMOFOIL HD Perf. BMF

™

ULTRAPHON™ ACOUSTITUFF™

Thickness (mm) 25 50 25 50 25 50 25 50 25 75 25 50 25 50 25 50

125 0.08 0.23 0.07 0.24 0.10 0.30 0.14 0.33 0.12 0.69 0.05 0.30 0.14 0.31 0.15 0.36

250 0.39 0.71 0.26 0.62 0.39 1.01 0.45 1.01 0.31 1.19 0.55 0.75 0.38 0.83 0.33 0.76

Frequency (Hz) 500 1000 2000 4000 0.73 1.02 1.12 0.84 0.99 1.09 0.97 0.78 0.65 0.93 1.04 1.03 1.00 1.07 1.12 1.15 0.79 1.00 1.01 1.00 1.31 1.20 1.05 0.97 0.99 0.97 0.55 0.29 1.17 0.99 0.64 0.34 0.81 1.09 1.09 0.91 1.15 1.09 1.03 0.92 0.65 0.90 0.70 0.50 0.90 0.85 0.65 0.50 0.87 1.07 1.06 0.90 1.16 0.99 0.90 0.78 0.74 0.94 1.03 1.04 1.19 1.09 1.03 1.04

Bradford Glasswool THERMOFOIL™ Premium HD Perf. DUCTLINER/ ACOUSTITUFF™ ULTRATEL™ 48kg/m3 Bradford THERMOFOIL™ FIBERTEX™ HD Perf. DUCTLINER BMF 60kg/m3 Bradford FIBERTEX™ 450 ULTRAPHON™ 50 0.43 0.99 1.09 1.11 1.04 1.03 ™ 80kg/m3 ACOUSTITUFF 50 0.54 0.99 1.07 0.81 0.57 0.33 * NRC: Arithmetic average of absorption coefficients of frequency 250, 500, 1000 and 2000Hz.

41

5000 0.75 0.59 1.00 1.17 0.95 0.95 0.25 0.28 0.89 0.90 0.50 0.60 0.79 0.73 0.98 0.90

NRC* 0.81 0.94 0.72 0.95 0.81 1.14 0.75 0.95 0.83 1.12 0.70 0.79 0.85 0.97 0.76 1.01

1.03 0.25

1.06 0.85


A C O U S T I C

D E S I G N

ATTENUATION OF LINED BENDS. The application of acoustic lining to bends can be very effective in attenuating duct-borne sound. Square elbows are preferred to radius bends. The lining should have a thickness at least 10% of D, the clear width between the two linings (refer diagram), and the length of lining should extend a distance not less than 2D before and after the bend. Table 17 gives attenuation in dB achieved by square elbows without tur ning vanes when lined as recommended.

FIG 37. SOUND ATTENUATION IN LINED PLENUM.

θ

d

FIG 36. SOUND ATTENUATION BY LINED SQUARE ELBOWS.

AIR FRICTION. The energy absorbed by frictional losses in the air handling system may be significant, particularly for high velocity systems. The following information will assist the designer in assessing the effect of duct liners upon frictional losses. The usual procedure for determining friction losses in air ducts is by use of the Air Friction Charts published by the ASHRAE Handbook of Fundamentals and the IHVE Guide. These charts provide friction losses for sheet metal ducts of standard construction. These losses must be multiplied by a factor to correct for the influence of duct liners. The following graph shows correction factors for the Bradford range of Glasswool and FIBERTEX™ Rockwool duct liners. It is based on actual tests on a lined duct of 460 x 200mm internal dimensions, equivalent to a 280mm diameter circular duct. To adjust the correction factor selected for ducts of other dimensions, increase by up to 10% for circular equivalent sizes down to 150mm and decrease by up to 10% for circular equivalent sizes up to 1000mm.

2D Lining Thickness (10% of D min.)

D

Acoustic Lining

TABLE 17. ATTENUATION BY LINED SQUARE ELBOWS, dB. D (mm)

63

Frequency (Hz) 125 250 500 1000 2000 4000 8000

125

1

6

12

14

16

1

6

12

14

16

18

1

6

12

14

16

18

18

6

12

14

16

18

18

18

250 500 1000

1

ATTENUATION BY LINED PLENUMS. The acoustical lining of fan discharge and suction plenums is often the most economical and convenient approach to achieving a major part of the sound attenuation required in a system. The following formula gives an approximate value of the attenuation achieved by this means (refer diagram). (cosθ) (2πd2)

+ So

1–α αSw

FIG 38. AIR FRICTION CORRECTION FACTOR. 2.0

Correction Factor

Attenuation = 10 log10 [So

G U I D E

]

1 1.5 2

1

Where: α = absorption coefficient of the lining

2

3

4 5 6 8 10 Air Velocity (m/s)

20

1 = Black Matt tissue (BMF) Faced Ductliners. 2 = THERMOFOIL™ Perforated Foil Laminate Faced Ductliners.

So = area of outlet opening, m2 Sw = total plenum wall area, m2 d = slant distance, centre inlet to centre outlet, m θ = angle of incidence at the outlet, degrees.

42


A C O U S T I C

D E S I G N

RESISTANCE TO AIR EROSION AND RECOMMENDED VELOCITIES Bradford Glasswool and FIBERTEX™ Rockwool ductliners have been tested for surface erosion at extreme velocities by the quantitative method developed by the CSR Building Materials Research Laboratories, based on Underwriters Laboratory Standard UL181-1990. The products were subject to velocities up to 40m/s and then a safety factor of 0.4 applied in accordance with the Underwriters Laboratory test. On the basis of these results and typical air friction correction factors from ASHRAE, the following maximum design velocities are recommended.

DUCT BREAK OUT-NOISE. Noise breakout from ducts can occur from: • Fan noise passing through the duct • Aerodynamic noise (also know as re-generated noise), from obstructions fittings etc in the duct • Turbulent airflow causing duct walls to vibrate and rumble radiating low frequency airborne noise. Solutions to reduce noise breakout from ducts: • Stiffer ducts (circular ducts are better than square or rectangular). External bracing of ducts increases stiffness, however it can improve the radiation efficiency of the duct cancelling the benefit of increased stiffness. • Using heavier material for duct walls and increasing damping (ie. thicker steel sheeting). • Adding damping (spray on or self adhesive compounds). • Acoustic lagging, preferably with a heavy limp impervious layer isolated or decoupled from the duct with either glasswool (such as Bradford ACOUSTILAG™) or rockwool. The solutions to reduce noise breaking out from ducts can be expensive. Therefore it is more cost effective to avoid noise break out problems than to try to correct them later.

TABLE 18. MAXIMUM DESIGN VELOCITY. Product

Maximum Design Velocity (m/s)

Bradford Glasswool Covered with Perforated Metal

23

Faced with Perforated Foil

18

Faced with Black Matt Tissue (BMF) Faced with ACOUSTITUFF™ Faced with ULTRAPHON™

22 30 26

Bradford FIBERTEX™ Rockwool FIBERTEX™ Ductliner CF covered with Perforated Metal

23

DUCT BREAK-IN NOISE. Noise inside ceiling plenums or from air conditioning equipment, plant rooms etc, can break into ducts, particularly flexible ducts and then be carried into rooms or spaces below. Flexible ducts, due to their light weight, flexibility, speed and ease of installation, are commonly used in air conditioning systems. Noise can more easily penetrate flexible ducts because of their lightweight nature. To avoid break-in noise, the following can be used: • Where possible, avoid ducts passing through noisy areas as this can significantly increase noise through the air conditioning system. • Replace lightweight flexible ducts with heavier ducting such as sheet steel. • The flexible ducts can be enclosed in a solid enclosure constructed from timber, plasterboard or sheet steel, etc. Before enclosing flexible ducts, it should be noted that noise in the ceiling cavity will most likely penetrate the ceiling. This will happen more so if lightweight lay-in tiles using metal grids are used. Fixed plasterboard ceilings give better acoustic performance than lightweight ceiling tiles.

FIBERTEX™ Ductliner with Perforated Foil18 FIBERTEX™ Ductliner faced with Black Matt Tissue (BMF)

G U I D E

22

EXTERNAL DUCT LAGGING. External lining (lagging) of air conditioning ducts with foil faced rockwool or glasswool reduces duct breakout noise by damping the duct. Some of the noise which breaks out through the lagged duct is absorbed by the surrounding insulation. The sound attenuation achieved inside the duct is also enhanced by duct lagging particularly at low frequencies, up to about 500Hz. Air handling ducts are commonly lagged using: • Bradford FIBERTEX™ Rockwool Ductwrap • Bradford Glasswool MULTITEL™ or FLEXITEL™ with Medium or Heavy Duty THERMOFOIL™. • Bradford Glasswool THERMOGOLD™ Ductwrap.

43


A C O U S T I C

D E S I G N

FLOW GENERATED NOISE. Turbulent noise in ducts is generated from the following: • Objects such as dampers, grilles, rods, etc. • Constrictions in duct cross sectional area, orifice plates, silencer splitters etc. • Jet noise, inlet or discharge noise flowing through orifices. • Boundary layer turbulence, air passing over the inner surface of the duct. • Flow around bends and duct take offs (branches). These sources cause turbulence in ducts and this noise is also known as re-generated noise. The intensity of the re-generated noise depends upon the velocity of the air in the duct.

G U I D E

FIG 39. LOCATION OR DUCT ATTENUATOR. Noise break-out from noisy side of attenuator Plant Room

Bad location

END REFLECTIONS. At the end of a duct (register, diffuser grille etc.) the air meets a large increase in volume. This allows expansion of the air providing useful sound energy losses at the low frequencies. This is termed ‘end reflection loss’. A higher number of small registers spaced well apart will transmit less low frequency noise into a room than one large single register.

Plant Room

Noise break-In to quiet side of attenuator

Bad location

DUCT ATTENUATORS OR DUCT SILENCERS. Duct attenuators or silencers are used where high attenuation is required. These silencers usually consist of sheet steel duct housing containing sound absorbent ‘splitters’ usually made of rockwool or glasswool. The silencer’s attenuation is normally quoted as an insertion loss in octave frequency bands. Silencers cause a pressure drop across them and also regenerated noise through the splitters, which increases with the air velocity through the ducts. Silencers should ideally be located where the duct leaves the plant room (see Figure 39). Care must be taken to avoid plant room noise from entering the quiet side of the silencer. Standard silencers incorporate a perforated metal screen backed by Bradford Glasswool or Bradford FIBERTEX™ Rockwool faced with black fibreglass tissue (BMT). An alternative design, particularly for smaller systems, is to face the r ig id insulation with Bradford ULTRAPHON™ wrapped or taped around the edges and glued into the C-channel supporting the frame. Test results are shown in Appendix C, Table C9. Bradford FIBERTEX™ Rockwool is recommended for high temperature attenuation such as hot gas exhausts.

Plant Room

Ideal (but ‘impractical’) location

Plant Room

Good practical location

44


A C O U S T I C

D E S I G N

FLANKING THROUGH AIR CONDITIONING DUCTS. Where two rooms are served by common ducts, sound (ie speech, machinery noise etc) can travel from one room and into the next room via the duct. In some buildings, speech can be heard through ducts. This is also known as ‘crosstalk’. ‘Crosstalk’ or sound through ducts can be attenuated by: • internally lining ducts with rockwool or glasswool. • increase the length of internally lined duct between offices. (Refer to Figure 40). • increase the amount of end reflection (more smaller registers are preferable to fewer larger registers). • fitting duct silencers. • modifications to room layouts to reduce ‘crosstalk’.

G U I D E

Products – Internal Duct Lining: The following glasswool blankets are generally used for internal duct lining: • Bradford SUPERTEL™ Glasswool (32kg/m3). • Bradford R-rated Ductliner (32kg/m3). • Bradford FIBERTEX ™ Rockwool Ductliner (60kg/m3). The above Glasswool blankets can be faced with: • ULTRAPHON™ (black glass cloth fabric) • ACOUSTITUFF™ (lightweight foil facing) • Heavy Duty THERMOFOIL™ 750P perforated, (optional: Mylar film between blanket and foil to prevent fibre release). • Fine, lightweight polyester films (Mylar or Melinex). • Black or clear fibreglass tissue. Products – External Duct Lagging: • Bradford THERMOGOLD™ Ductwrap (18kg/m3). • Bradford MULTITEL™ Glasswool (18kg/m3) with Medium Duty THERMOFOIL™. • Bradford FLEXITEL™ Glasswool (24kg/m3) with Medium Duty THERMOFOIL™. • Bradford FIBERTEX™ Rockwool Ductwrap (50kg/m3) with Medium Duty THERMOFOIL™. • Bradford ACOUSTILAG™ 20 or 23.

FIG 40. DUCTWORK LAYOUT TO REDUCE CROSSTALK.

Layout To Be Avoided Air Flow

Crosstalk

Crosstalk path

Crosstalk path

Crosstalk path

Crosstalk path

Preferred Layout Air Flow

45


A C O U S T I C

D E S I G N

G U I D E

Bradford Acoustic Solutions for Specialty Applications. Home Cinema.

• Ceilings should include increased mass to increase their STC rating. Multi layers of CSR Gyprock® plasterboard can be used with Bradford Rockwool or Glasswool Ceiling Batts above.

The current trend in households today is the use of timber floors or tiled floors which are hard and acoustically reflective. These together with reflective walls and ceilings result in long reverberation times not suited to home cinema systems.

• Floors should be insulated with Bradford Floor Batts particularly if the cinema room is upstairs. (see Floor/Ceiling Noise Control Systems, Appendix B).

Under these circumstances, home cinema systems will require more sound absorption in the room to lower the reverberation time closer to the optimum level suited to amplified music and speech. Note that too much absorption will make the room ‘dead’ and result in poorer quality sound.

• Windows should be double glazed with preferably different size laminated glass panes to provide better damping. Large air gaps between the glass panes, and properly sealed around the perimeter of the frame also increases the window’s acoustic rating. Laminated single pane glass is the next best choice.

To lower the reverberation time of a room, install:

• Doors should be solid core timber or metal with good quality door seals. Preferably double doors or an insulated sound lock should be used.

• Decorative fabric faced rockwool or glasswool absorbers on the walls. • Velour coated high density rockwool or glasswool on the walls.

Note that if the room has ducted air conditioning, then flanking can occur through the ducting and sound can pass into the next room.

• Perforated timber, Gyprock® plasterboard or perforated metal pan ceiling with rockwool or glasswool insulation above.

Bradford Products for – Walls:

• Rugs, carpet, curtains and soft furniture in the room.

• Bradford Rockwool or Glasswool Partition Batts.

The acoustic reproduction of many modern home cinema systems is very good, and they can generate high levels of bass sound which penetrates building materials more easily. Low frequency sound is also more difficult to absorb.

• Bradford SoundScreen™.

Ceilings: • Bradford Rockwool or Glasswool Ceiling Batts.

Therefore the home cinema system room may be a source of noise for others in the household or neighbours, particularly if the volume is loud. These rooms should be treated or ‘sound proofed’ if they are likely to cause disturbance to others. The following treatments should be considered:

• Bradford Glasswool Ceiling Panel Overlays. • Bradford Rockwool FIBERTEX™ 350, 450. • Bradford Glasswool FLEXITEL™, SUPERTEL™, ULTRATEL™. • Bradford Glasswool Absorption Blanket.

• Brick veneer walls should use mutli-layers of CSR Gyprock® Fyrchek™ or Soundchek™ plasterboard to add mass and increase the STC of the walls. Ideally, the wall should have two separate studs with Bradford Rockwool or Glasswool Partition Batts inside the cavity walls. Bradford batts inside cavity partitions can increase the walls acoustic rating by STC 10. If this is not possible then staggered studs or the widest stud cavity available should be used and filled with Bradford Rockwool or Glasswool Partition Batts.

46


A C O U S T I C

D E S I G N

G U I D E

• Sound absorbing panels consisting of fabric faced Bradford Rockwool or Glasswool. The decorative facing chosen should be acoustically transparent (with low flow resistance) to maximise sound absorption within the insulation. Decorative open weave fabrics are suitable for these acoustic applications.

Auditoriums. Auditoriums are a specialised area of room acoustics with many books written on the subject. The acoustic design of auditoriums should be undertaken by an experienced acoustic consultant. This is a simplified guide to the acoustic requirements of auditoriums.

• Bradford ACOUSTICLAD™ is ideal broad band industrial grade absorber which can be used in auditoriums.

The shape and size of an auditorium can have a great influence of the acoustics of the space. It is also very important to control the auditorium’s reverberation time so the users can experience good acoustics. General purpose auditoriums can have multiple uses such as speech and amplified music which have conflicting reverberation times.

• Bradford Rockwool or Glasswool behind spaced timber panels (slotted or slatted). The sound travels through the gaps in the timber and is absorbed by the insulation. • Alternative treatments include fixing the sound absorbing batts behind perforated panels, such as plywood, Gyprock® plasterboard or metal. The use of a BMF (Black Matt Facing) tissue or Bradford ULTRAPHON™ on the insulation is recommended for aesthetic reasons.

The acoustic designer needs to determine the auditorium’s optimum reverberation time for its intended use. Computer software is available that allows modelling the optimum reverberation time for the room. Sound absorbing materials are added to the rooms surfaces to fine tune and optimise the room’s reverberation time. Artificial reverberation can be added either acoustically or electronically to modify the sound.

• Membrane or panel absorbers – typically solid, reflective panels (timber, plasterboard etc.) fixed to walls on studwork. Panel absorbers can be tuned to resonate (absorb) sound within a narrow frequency range. Adding rockwool or glasswool insulation in the air cavity of panel absorbers, increase their absorptive frequency range.

The relationship between reverberation time and sound absorption is given by the Eyring’s equation (refer to Reverberation Control, page 63). There are a number of methods used to absorb sound in an auditorium. These include:

FIG 41. TYPICAL ACOUSTIC TREATMENTS FOR AUDITORIUM WALLS AND CEILINGS. Acoustic Absorbing Panels on walls Bradford Partition Batts

Bradford Acousticon Roofing Blanket

Bradford Ceiling Batts

47


A C O U S T I C

D E S I G N

• Cavity absorbers – are usually an enclosed volume of air with a small neck/opening (often known as Helmholtz resonators. Cavity absorbers provide a very narrow band of sound absorption, which can be expanded with the use of rockwool or glasswool in the air space. These absorbers have specialised acoustic applications such as studios and auditoria, and for pure tone absorption.

G U I D E

Products. • Bradford Glasswool or Rockwool Partition Batts. • Bradford FIBERTEX™ Rockwool. • Bradford Glasswool MULTITEL™, FLEXITEL™, SUPERTEL™ or ULTRATEL™. • Bradford FIBERTEX ™ Rockwool Ductliner (60kg/m3). • Bradford ACOUSTICLAD™.

• Perforated metal ceiling panels with rockwool or glasswool insulation above. The size, number of perforations, insulation type, thickness and density can affect the frequency at which maximum absorption occurs.

• Bradford Rockwool or Glasswool Ceiling Batts. • Bradford Glasswool ACOUSTICON™. • Bradford Rockwool or Glasswool Ductliner. • Bradford ACOUSTILAG™ 23 or 26.

On occasions, auditoriums have dual uses, for example speech and amplified music. It is possible to introduce absor ption into these auditor iums to lower the reverberation time to suit the acoustic requirements. Temporary absorbing panels can be introduced in the form of sliding acoustic doors, or portable architecturally designed sound absorptive structures to suit the decor of the auditorium.

Insulation facings: • Bradford THERMOFOIL™ (Light, Medium and Heavy Duty or Heavy Duty perforated). • Bradford THERMOTUFF™ foil. • Bradford ULTRAPHON™. • Bradford ACOUSTITUFF™. • Black or clear fibreglass tissue.

Sound absorption is often required on the rear wall of the auditorium to stop unwanted reflection of sound. The personal address system amplifier, type and size of microphones, number of speakers, sound delay, etc., also need to be considered.

Sports Complexes. Sporting complexes can suffer from poor acoustics due to the high reverberation times caused by the lack of sound absorptive finishes within the space. This can result in difficulty understanding speech.

It is important to stop unwanted noise from entering the auditorium from people, air conditioning, road and rail traffic, aircraft, public amenities, foyers, rain etc.

Sporting complexes therefore, require sound absorptive material to be added to achieve a lower reverberation time suitable for speech. (Refer to Table A5, page 64).

To reduce extraneous noise from entering the auditorium: • Fill any wall cavities with Bradford Rockwool or Glasswool Partition Batts.

The following describes ways to add sound absorption in a sporting complex:

• Install Bradford ACOUSTICON™ foil faced roofing blanket under steel roofing to reduce rain noise by up to 18dB(A). Refer to Rain Noise Reduction with Metal Deck Roofing, page 20.

• Fabric faced rockwool or glasswool acoustic absorbers for the walls. • Velour coated high density rockwool or glasswool absorbers for the walls.

• Internally line air conditioning ducts with rockwool or glasswool (either using foil facing, fine fibreglass tissue, Bradford ACOUSTITUFF™ or ULTRAPHON™. Externally lag ducts with rockwool or glasswool faced with Bradford Thermofoil™ facing. Consider the use of duct silencers to reduce air conditioning noise levels.

• Bradford ACOUSTICLAD™ wall/ceiling absorber. • Porous absorbers such as rockwool or glasswool insulation with a perforated facing of; metal, timber, or Gyprock® plasterboard etc. The use of a fine fibreglass tissue facing BMF (Black Matt Facing) tissue or Bradford ULTRAPHON™on the insulation can be used for aesthetic reasons and eliminates fibre release. Bradford ACOUSTICLAD™ wall and ceiling absorber is durable and its high acoustic absorption is an excellent choice for sports complexes. ACOUSTICLAD™ offers excellent test results with NRC ranges from 0.9 to 1.05.

• Locate the plant room of the air conditioning system away from the auditorium. If this is not possible, then acoustically treat the plant room with high STC walls, roof/ceiling, floors, doors etc. • Lag waste pipes inside auditorium with Bradford Acoustilag™ 23 or 26. • Install acoustic door seals on door perimeters or absorbent ‘sound locks’.

48


A C O U S T I C

D E S I G N

G U I D E

FIG 42. TYPICAL ACOUSTIC TREATMENTS FOR SPORTS COMPLEX. Bradford Partition Batts Bradford Acousticon Roofing Blanket


Bradford Acoustic Baffles

Bradford Wall Batts

• Bradford Rockwool or Glasswool behind spaced timber panels (slotted or slatted). The sound enters the insulation through the gaps in the timber and is absorbed by the insulation.

It is advisable to consult an acoustic consultant for vibration isolated flooring systems. If the sports complex is on a second storey of a building, install Bradford Rockwool or Glasswool Ceiling Batts beneath the complex’s floor in the floor/ceiling cavity.

To reduce rain nose under metal roofing, install Bradford ACOUSTICON™ foil faced roofing blanket under the metal deck. This can reduce rain noise by up to 18dB(A) and improve the STC rating of the roof.

Bradford Products. • Bradford ACOUSTICLAD™ wall/ceiling absorber.

To reduce timber floor impact noise, use a resilient materials such as rubber, dense rockwool or glasswool, rubber/cork compounds etc., beneath the battens or floor joists and the floor supports.

• Bradford FIBERTEX™ ROCKWOOL. • Bradford Glasswool FLEXITEL™, SUPERTEL™ or ULTRATEL™ with optional BMF, ULTRAPHON™or THERMOFOIL™ facings.

For existing floors, a floating floor can be constructed above the existing floor with a resilient material layer between the two flooring systems. The correct stiffness of the damping layer should be selected for both the static and dynamic loads. The two floors should not be mechanically fixed with nails or screws as this would make the damping material redundant.

• Bradford ACOUSTICLAD™. • Bradford Glasswool ACOUSTICON™. • Bradford Rockwool or Glasswool Ceiling Batts.

49


A C O U S T I C

D E S I G N

Canteens/Restaurants.

G U I D E

Fyrchek on walls and ceilings, with Bradford Rockwool or Glasswool Partition/Ceiling Batts installed. Heavier glazing and addressing flanking paths should also be considered. (Refer to additional information detailed for Walls, Roof/Ceilings and Floors). ™

Canteens and restaurants that have hard floors, walls and ceilings, are very reverberant, especially when full of diners and music. Noise is generated from voices and cutlery. Often soft music is used to provide an ambience and some acoustic masking.

Products. • Bradford FIBERTEX™ Rockwool.

These noise sources make communication difficult, and people tend to raise their voices to be heard, which in-turn increases the noise level in the room.

• Bradford Glasswool or Rockwool Partition Batts. • Bradford Glasswool FLEXITEL™ SUPERTEL™ or ULTRATEL™ with BMF or ULTRAPHON™.

Canteens and restaurants can benefit from added sound absorption in the room to control reverberation.

• Bradford ACOUSTICLAD™.

To lower the reverberation time within a canteen or restaurant, install:

• Bradford ACOUSTICON™.

• Fabric faced rockwool or glasswool absorbers on the walls.

Karaoke & Nightclubs.

• Bradford ACOUSTICLAD™ perforated metal wall absorber with rockwool or glasswool insulation (encapsulated in a thin polyester film such as Mylar or Melinex to stop fibre release).

Karaoke Rooms and Nightclubs will require reverberation times optimised for music. Amplified music played in these venues has considerable low frequency ‘bass’ energy. To optimise the acoustics, the reverberation times should be slightly longer at the lower frequencies.

• Perforated timber, Gyprock® plasterboard or perforated metal pan ceiling with rockwool or glasswool insulation above. Insulation should be encapsulated to stop fibre release.

To control reverberation in these rooms use: • Porous absorbers – Fabric faced rockwool or glasswool absorbers for the walls.

Note that too much absorption may make the room acoustically ‘dead’, and can result in a lack of acoustic privacy for diners.

• Perforated timber, Gyprock® plasterboard or perforated metal pan ceiling with rockwool or glasswool insulation above.

If the canteen or restaurant has a noise sensitive area above, below or adjacent to it, the facades should have higher acoustic performance (STC ratings) to stop noise ‘breaking-out’, ie. multi-layers of heavier Gyprock®

• Bradford ACOUSTICLAD™ perforated metal panel ceiling system. • Membrane or panel absorbers.

FIG 43. TYPICAL ACOUSTIC TREATMENTS FOR CANTEEN/RESTAURANT APPLICATIONS.

FIG 44. TYPICAL ACOUSTIC TREATMENTS FOR KARAOKE ROOM/NIGHTCLUB APPLICATIONS.

Bradford Insulation in partition walls

Bradford Insulation in partition walls

Bradford Acoustic Wall Absorbers

Bradford Acoustic Wall Absorbers

Bradford Acousticon under metal deck roof

Bradford Insulation above perforated ceiling system

Bradford Insulation above perforated ceiling system

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Flanking paths should also be considered when acoustically isolating rooms requiring high STC ratings. Sometimes these flanking paths can be the limiting factor in obtaining acoustic privacy from room to room.

Karaoke rooms and nightclubs can cause disturbance for others nearby as music sound levels inside can reach or exceed 100dB(A). These rooms should be ‘sound proofed’ if they are likely to cause disturbance to others. To do this, building envelopes with very high STC ratings are required.

It is advisable to engage the services of an acoustic consultant to design sound proofing for rooms with very high noise levels, in particular, Karaoke rooms and nightclubs.

The following acoustic treatments are recommended.

WALLS. Use multiple layers of CSR Gyprock Fyrchek ™ plasterboard to add mass and increase the STC of the walls. (The more mass that is used, the higher the STC rating). Ideally, the wall should have two separate studs with Bradford Rockwool or Glasswool Partition Batts inside the cavity of the walls for an increase of up to 10 STC. If this is not possible, then staggered studs or the widest possible stud cavity should be used (to reduce low frequency sound transmission) and filled with Bradford Rockwool or Glasswool Partition Batts.

Products. • Bradford Rockwool FIBERTEX™ 350, 450. • Bradford Glasswool FLEXITEL™, SUPERTEL™, ULTRATEL™. • Bradford Glasswool Absorption Blanket. • Bradford Glasswool Ceiling Panel Overlays. • Bradford Rockwool or Glasswool Partition Batts. • Bradford ACOUSTICLAD™.

Shopping Centres.

CEILING. Ceiling should have extra mass added to increase the STC. Multi layers of CSR Gyprock® plasterboard can be used with Bradford Rockwool or Glasswool Ceiling Batts above. Beneath the plasterboard ceiling, a suspended perforated metal pan ceiling can be used to provide sound absorption in the room.

In shopping centres, the designers should look at noise control in the following areas: • Between shops to provide acoustic privacy – refer to sections in this book on wall and ceiling insulation. • Reverberation control – within the shopping centre open areas (ie. stage and dining areas).

WINDOWS. Windows should be double glazed with preferably different size laminated glass panes (laminated glass has better damping). Air gaps between the glass panes should be properly sealed around the perimeter. Thicker laminated single pane glass is the next best choice.

• Rain noise under steel roofing – install Bradford Acousticon™ hard under steel deck roofing. • Air conditioning and mechanical services noise – acoustically treat plant room, internally line and externally lag air conditioning and air extraction ducts, particularly where they are exposed. Plant rooms should use high STC rating walls, ceilings and floors if next to noise sensitive areas. Plant room walls should be lined with Bradford Acousticlad™ to absorb noise.

DOORS. Doors should be solid core timber or metal with good quality acoustic door seals. An insulated ‘sound lock’ using acoustically treated doors will provide better acoustic performance. Note that for higher STC walls, ceilings and floors, flanking must be considered. (Refer to ‘Flanking Paths’, page 59). Some Karaoke restaurants/clubs have many Karaoke booths which require acoustic isolation from each other. It is recommended that high STC rating walls are used to acoustically isolate these rooms from each other. Refer to the CSR Gyprock Fire & Acoustic Design Guide, NºGYP500 to choose a wall system.

• Carpark noise – avoid steel speed humps which work lose with time and become noisy. Products. • Bradford Rockwool or Glasswool Partition Batts. • Bradford FIBERTEX™ Rockwool. • Bradford Glasswool SUPERTEL™, ULTRATEL™. • Bradford ACOUSTICON™. • Bradford ACOUSTICLAD™.

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Music Rooms, Recording Studios, Radio & Television Rooms.

G U I D E

FIG 45. OPTIMUM REVERBERATION TIMES FOR MUSIC/TV/RADIO STUDIOS. 1.6 1.4 Reverberation Time (sec)

The optimum reverberation time required in a music studio depends on the size of the room. Music recording studios and radio or television broadcasting rooms require very short reverberation times or a ‘dead’ acoustic environment. To achieve shorter reverberation times with smaller room volumes, more sound absorption is required. The reverberation times for the room should be set for each octave or more accurately each 1/3 octave band. Generally for music, the lower frequencies require higher reverberation times. For speech the reverberation time should be approximately equal across frequency bands. The relationship between reverberation time and sound absorption is given by the Eyring’s equation (refer to ‘Reverberation Control’ page 63).

1.2

io

ud

1.0

sic

St

u

M

0.8

tudio

alk S TV/T

0.6 0.4 0.2 0

50

0

0

10

30

00

00

10

50

0

00

10

Room Volume (m3)

If steel roofing is used for these rooms, insulate the roof with Bradford ACOUSTICON™ to reduce rain noise transmission. Ceilings should also use multi layers of CSR Gyprock® Fyrchek™ resiliently mounted to the furring channels.

Sound absorbers do not absorb sound equally in each frequency band. Therefore it is common practice to use a combination of different types of absorbers.

Windows should be double glazed with preferably:

There are various types of sound absorbers, including:

• Different size laminated glass panes (laminated glass has better damping).

• Porous type absorbers eg. Acousticlad , fabric faced absorbers, perforated metal pan ceilings and moulded foam etc. ™

• Large air gap between the glass. • Properly sealed around the perimeter of the frame.

• Panel absorbers (Refer to ‘Room Acoustics’, page 64).

Doors should be solid core timber or metal with good quality door seals. Preferably double doors or an insulated sound lock should be used.

• Cavity absorbers (Helmholtz resonators). The above types add sound absorption inside the room, and are required, to tune the reverberation time as close to optimum for music or recording purposes.

Recording studios, radio and television broadcasting rooms should also be vibration isolated from the main building structure. This will reduce the transfer of low frequency noise into the space which can affect the acoustics of these rooms. Roads, railway lines, industry etc, can be sources of low frequency noise and vibration.

It is imperative that extraneous noise does enter into recording studios, radio or television broadcasting rooms. Therefore it is imperative that these rooms are properly sealed or ‘sound proofed’. Very high STC walls, doors, windows, roof/ceilings are required.

It is advisable to engage the services of an acoustic consultant to design sound proofing for TV/Radio/Music Studios.

Walls should use mutli-layers of CSR Gyprock Fyrchek™ with preferably two separate studs to support the walls. Bradford Rockwool or Glasswool Partition Batts should fill the cavity of the walls for an increase of up to 10 STC. ®

TABLE 19. RECOMMENDED MAXIMUM BACKGROUND SOUND PRESSURE LEVEL FOR STUDIO APPLICATIONS. 31.5 Studio Use

63

Octave Band Sound Pressure Level (Hz) 125 250 500 1000 2000 4000

8000

Recommended Maximum Background Sound Levels [dB]

Drama and Music Studios

65

47

37

29

24

20

17

15

13

Television and Talk Studios

70

52

42

34

29

25

22

20

18

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Products.

FIG 46. TYPICAL ACOUSTIC TREATMENTS FOR TV/RADIO/MUSIC STUDIO APPLICATIONS.

• Bradford FIBERTEX™ Rockwool. • Bradford Glasswool SUPERTEL™ or ULTRATEL™.

Bradford Insulation treatment to air conditioning ducts

• Bradford ACOUSTILAG™. • Heavy duty perforated THERMOFOIL™.

OEM. CSR Bradford Insulation supplies the full range of glasswool and rockwool products to original equipment manufacturers (OEMs). Bradford insulation is used for acoustic or thermal purposes, and adds value to OEMs’ products. Glasswool can be used for the following requirements: • Thermal. • Acoustic. • Fire resistance.

Bradford Insulation in high STC partition walls

CSR Bradford Insulation supplies many OEMs, and each has unique requirements for rockwool and glasswool insulation products.

Bradford Acoustic Absorbers to control reverberation

OEMs should contact the CSR Bradford Insulation Office in their reg ion to discuss their specific requirements.

Products. • Bradford Glasswool FLEXITEL™, SUPERTEL™, ULTRATEL™.

Products.

• Bradford FIBERTEX™ Rockwool.

• Bradford Rockwool.

• Bradford ACOUSTICLAD™.

• Bradford Glasswool.

References.

Heavy Plant.

1 Sound Research Laboratories, Noise Control in Building Services, Pergamon Press, First Edition 1988.

Engine compartments of plant and machinery should be lined with Bradford Rockwool or Glasswool faced with Bradford Heavy Duty 750P THERMOFOIL™ Perforated to absorb engine and ancillary noise. As engine noise has most energy at low frequencies, insulation thickness should be at least 75mm. The thicker the insulation, the better the low frequency sound absorption.

2 Bruel & Kjaer, Noise Control, Principles & Practice, Naerum Offset, Second Edition, 1986. 3 D.A Bies & Hansen, Engineering Noise Control, E & FN Spon, Second Edition, 1996. 4 L.L Beranek, Noise And Vibration Control, Institute of Noise Control, Revised Edition, 1988.

Lightweight sheet steel casings can often vibrate and emit noise. To damp these casings, Bradford ACOUSTILAG™ can be used. The glasswool side of the Acoustilag should be secured firmly to the outside of the sheet steel to increase the panel’s mass. The mass of the loaded vinyl, damps the vibrating panel, and reduces noise. Operators cabins should also be fully enclosed and well sealed to stop noise from entering. Dust inside an operator cabin is a good indication the cabin is poorly sealed. Cabins should also be vibration isolated for operator comfort and safety, and also to minimise re-radiated noise from lightweight materials. The cabin can be lined with rockwool or glasswool insulation with a suitable facing such as perforated THERMOFOIL™ to absorb noise within the cabin. 53


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APPENDIX A.

The Nature of Sound. Introduction.

sounds with frequencies above 15kHz, and frequencies above 10kHz are rarely significant for sound control purposes.

For most of us, sound is simply something we hear. It is the sensation which results from vibrations in the air interacting with the hearing mechanism of our ears. Noise is by definition, unwanted sound. It may be unwanted because it is damaging, dangerous, annoying, or detracts from wanted sounds.

Sound waves are not limited only to the audible range. Higher frequency sound -’ultrasound’- (greater than 20kHz) has many applications in medicine and industry, while lower frequency sound – ‘infrasound’ (lower than 20Hz) appears as undesirable structural vibrations.

‘Sound’ is also used as a general term to describe the vibrations or pressure variations which give rise to the ‘sound’ we hear. Throughout this guide, sound will be used in the general sense.

FIG A1. VIBRATION CREATES SOUND WAVES.

Sound moves through the air as a longitudinal pressure wave. These waves are caused either by vibrating surfaces or fluctuations in air flow. The process may be illustrated by considering what happens when we listen to sound from a radio, TV set, or public address system.

Air moves towards load speaker as cone moves backwards.

The loudspeaker is made to vibrate by an electrical signal. This causes a sympathetic vibration in the air as shown in Figure A1. When the air borne vibration reaches the ear drum, the reverse process applies, causing the ear drum to vibrate, stimulating the hearing system.

Air pushed away from loudspeaker as cone moves forwards.

FIG A2. TYPES OF TRAVELLING WAVES.

Sound flow is described as a wave, because it is the vibration that moves through the air. Individual air particles only vibrate on the spot with no net movement.

(a) Longitudinal Wave Direction of wave travel

This is similar to what happens when a stone is thrown into a pool of water. Ripples move outwards through the water, but individual particles of water only move up and down as the ripples pass. This is evidenced by observing any objects floating on the pool surface, and noting that they remain stationary. Sound waves are said to be longitudinal because the movement of air particles is in the same plane as the direction of flow as shown in Figure A2(a). This is different from water waves, where the movement of water particles is perpendicular to the direction of flow as shown in Figure A2(b). Water waves are known as transverse waves.

Vibration of particles

(b) Transverse Wave Direction of wave travel

Vibration of particles

The basic characteristics of sound are discussed below.

Frequency.

With the exception of musical notes, sounds consisting of only one frequency are extremely rare. Most of the sounds encountered in everyday life are a complex combination of many frequencies. It is totally impractical to characterise a complex sound by all its frequencies, so the concept of frequency ‘bands’ is introduced. The most common of these is the octave band, which has its upper frequency band exactly double the lower band.

Frequency is the rate of vibration. It has the units of Hertz (Hz) or ‘cycles per second’ where a cycle is one complete vibration to and fro. The range of human hearing - the so-called ‘audible range’ - extends from 20 to 20,000Hz (20kHz). In practice, few adults can hear

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The Sound Power Level is generally denoted Lw. Abbreviations such as SWL or PWL are also used. It is defined as:

All frequencies between these bands are then grouped together into the octave band. An octave band is described by its centre frequency which is the geometric mean of the upper and lower bands. The octave bands used for sound measurement are listed in Table A1.

Equation Nº1 Lw = 10 log10

TABLE A1. STANDARD FREQUENCY BANDS. Band Limit Frequency (Hz)

1/3 Octave Centre Frequency (Hz)

44 57 71 88 113 141 176 225 283 353 440 565 707 880 1130 1414 1760 2250 2825 3530 4400 5650 7070 8800 11300

50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000

Sound power source (W) Reference power (1 x 10-12 W)

and expressed in decibels (dB)

Octave Band Centre Frequency (Hz)

A Sound Power of 10 Watts therefore has a sound power level of: Lw = 10 log10

63

10 1 x 10-12 W

= 10 log 1013 125

= 130dB Similarly, a sound power of 1 Watt corresponds to a sound power level of 120dB, and a sound power of 1 milliwatt corresponds to a sound power level of 90dB.

250 500

Intensity is a measure of sound power flow per unit area and is expressed in units of Watts per square metre (W/m2). It is sound intensity at the ear which determines how loud a particular noise seems – the greater the intensity, the louder the noise heard.

1000 2000

Sound Pressure.

4000

Sound intensity cannot be directly measured. However, sound intensity is related to sound pressure (which is easily measured) according to Equation Nº2.

8000

Equation Nº2

Energy, Power and Intensity.

I

Sound waves transmit energy from a source to a receiver, e.g. from a loudspeaker to a listener’s ear. In some cases this is desirable, e.g. Iistening to music. In others, the emission of sound energy indicates inefficient machine operation, and is harmful or annoying to exposed people.

=

p2 z

Where: I = Intensity. p = Pressure due to sound wave. z = ρc = Acoustic impedance of air. ρ = Density of air. c = Speed of sound (344 m/s).

The rate at which a sound source emits energy is called its sound power, measured in Watts (W). The sound power range is extremely large, ranging from about 1 nanowatt (1 x 10-9 W or 0.000000001 W) for rustling leaves to well over 1 megawatt (106 W or 1,000,000 W) for violent explosions.

The sound pressure can be measured using a microphone which converts the pressure wave to an electrical signal that can be easily measured with a galvanometer. Instruments are built specially for this purpose and are known as Sound Level Meters.

This range of over 1015 W is difficult to handle, so a more suitable scale has been devised. This scale is the Sound Power Level scale which measures sound power logarithmically. This is especially appropriate, as the human ear responds to ratio changes in sound power, rather than to magnitude changes. To the ear, a change from 10 Watts to 1 Watt is equivalent to a change from 1 Watt to 0.1 Watt. 55


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high frequency sounds. Sound pressure levels measured with an ‘A’ – weighting network are expressed in A – weighted decibels or dB(A). Because the ‘A’ – weighted sound pressure levels takes account of the ear’s sensitivity to sound, most noise control legislation is written in terms of dB(A) levels.

Like sound power, sound pressure is expressed on a logarithmic scale known as the Sound pressure level, generally denoted Lp. Sometimes the abbreviation SPL is also used. Sound Pressure Level is defined as: Equation Nº3 Lp =

20 log sound pressure (measured in Pa)

Where noise levels fluctuate markedly with time (such as stamping machines, traffic on a busy roadway, etc.) it is now common to measure an ‘equivalent continuous sound pressure level’, denoted Leq. This is the sound pressure level of a steady sound which, over a given time period, would have conveyed the same acoustic energy as did the time-varying sound. Many sound level meters are able to automatically measure equivalent sound pressure level.

Reference sound pressure (2 x 10-5 Pa)

and, like sound power level, is expressed in decibels (dB). The reference sound pressure of 2x10-5 Pa represents the ‘threshold of hearing’. Thus a sound pressure level of 0dB indicates the quietest sound likely to be detected by young, healthy ears. At the other end of the scale, a sound pressure level of 130dB (a sound pressure of 63 Pa) represents the ‘threshold of pain’. Some typical sound pressure levels are shown in Table 2.

Other measures of sound level that are applicable to long-term variable noise (such as motor traffic) are denoted Lx where x is a number between 1 and 100.

TABLE A2. TYPICAL SOUND PRESSURE LEVELS. Noise Source

This is the sound pressure level which is exceeded for x% of the time. The L1, L10, L50 and L90 levels are the most commonly encountered. These statistical levels can be measured with more sophisticated portable sound level meters. Alternatively, statistical analysis or graphical techniques can be used to determine the statistical levels.

Sound Pressure Level (dB re 20 µPa)

Near Air Force Jet at take off

140

(Threshold of pain)

130

Pneumatic chisel

120

Angle grinding metal

110

Electric train crossing bridge

100

Petrol lawn mower

90

Average road traffic

80

Ringing telephone

70

Conversational speech

60

Analytical laboratory

50

Professional office

40

Residential area at night

30

Rustle of leaves

20

Breathing

10

(Threshold of hearing)

0

G U I D E

Addition of Decibels. As the decibel scale is logarithmic, two noise levels Lp1 and Lp2 values cannot be added in the same way as ordinary numbers. Consider for example, the sound power level of two machines, each with a sound power level of 120dB. From Equation Nº1 it can be calculated that the actual sound power of each source is 1 Watt. Thus their combined power will be 2 Watts which, according to Equation Nº1, corresponds to 123dB. Doubling the sound power results in an increase of 3dB in the sound power level. Adding a third machine of the same power would increase the total sound power to 3 Watts, which gives a sound power level of 125dB, while a fourth machine bringing the total sound power to 4 Watts would increase the sound power level to 126dB. Note again that doubling the sound power from 2 Watts to 4 Watts also increased the sound power level by 3dB (123dB to 126dB).

The sound pressure level then is used as the basic measure of quantity of sound. Levels can be measured right across the whole audible frequency range or in discrete octave or third-octave bands. ‘Weighted’ sound pressure levels may also be measured, of which the most common is the ‘A’ – weighted sound pressure level. ‘A’ – weighting adjusts the sound pressure to allow for the frequency response of the human ear. The ear is less sensitive to lower frequencies than to frequencies in the middle to high range. ‘A’ – weighting therefore decreases the level of low frequency sounds relative to middle and

This may seem complicated but there is a simple rule of thumb which is sufficiently accurate for all practical purposes:

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A C O U S T I C Difference between noise levels

D E S I G N

FIG A3. BEHAVIOUR AT SOLID BOUNDARIES.

Add to higher level (dB)

0 or 1

3

2 or 3

2

4 to 9

1

10 or more

0

G U I D E

Re

fle

cte

dS

ou

nd

Absorbed Sound sm

For the example above, 120dB + 120dB Add 3dB to 120dB

n Tra

Incident Sound

Tra n

sm

0dB difference = 123dB

123dB + 120dB Add 2dB to 123dB


125dB + 120dB Add 1dB to 125dB


Behaviour of Sound.

So

itte

dS

ou

nd

lec

f

Re

S ted

ou

nd

d

un

d itte

Sound Transmission.

Sound from a theoretical point source will radiate equally in all directions. As a result, the sound intensity will be inversely proportional to the square of the distance from the source. This means the sound pressure level will reduce by 6dB for each doubling of distance from the source. This generally applies outdoors in the free field. Thus, if Lp = 80dB at 4 metres from the source, it will be 74dB at 8 metres, 68dB at 16 metres, 62dB at 32 metres, as shown in Figure A2.

Sound striking a solid surface can cause the surface to vibrate, just as the ear drum vibrates when it is met by a sound wave. This vibration which is of the same frequency as the sound wave may set up another air-borne sound wave on the other side of the solid. The ability of a solid structure to resist sound transmission is called ‘acoustic insulation’. This is analogous to thermal insulation being the ability of a material to resist heat flow and electrical insulation being the ability to resist the flow of electricity. It is important to note that the mechanism involved in resisting these various flows is not universal.

This assumes that there is no interference with the sound flow such as buildings etc, and the further one gets from the source the more likely it is that some interference will occur. The most common interference is provided by a solid boundary. Sound striking a solid boundary may be either transmitted, reflected, or absorbed, as shown in Figure A3.

The fact that a material is a good thermal insulation does not indicate whether it is of any use as an electrical or acoustic insulator. Acoustic insulation is expressed as the difference in decibels between the sound pressure levels on the source and receiving sides of the structure. When discussing the performance of building elements, acoustic insulation is referred to in terms of ‘sound transmission loss’ (STL) or ‘sound reduction index’.

FIG A2. SOUND RADIATION FROM POINT SOURCE.

For all practical building elements, the sound transmission loss varies with frequency (Figure A5). There are essentially three modes: 1. At very low frequencies the sound reduction depends on the stiffness of the partition and natural resonances in the structure. The stiffer the panel, the more resistant it is to bending. As the frequency increases, the stiffness effect diminishes and the onset of resonances occur in the panel which lowers the acoustic performance of the panel.

80dB @4m 74dB @8m

68dB @16m

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2. At mid frequencies sound reduction increases by approximately 6dB for each doubling of frequency (6dB per octave) or mass per unit area.

FIG A5. THE ‘MASS LAW’ OF SOUND INSULATION. 60

3. At high frequencies sound transmission is influenced by the ‘coincidence dip’, which is a form of coupling between the sound waves in the air and the bending waves in the panel, resulting in efficient transfer of sound energy. The coincidence effect is a form of resonance which occurs at the critical frequency and tends to reduce the acoustic performance of the building element.

55

Average Sound Transmission Loss (dB)

50

FIG A4. TYPICAL SOUND TRANSMISSION LOSS CHARACTERISTIC FOR BUILDING PARTITIONS.

6dB per octave

G U I D E

45 40 35 30 25 20 15

Coincidence Dip

Transmission Loss

10 5 0

Stiffness controlled

1

2

3

4

5

7

10

20 20 40 50 70 100 200 300 400 500 700 000 1

Surface Density (kg/m2)

Mass controlled Critical frequency

recently released AS/NZS1276.1:1999 ‘Acoustics Rating of Sound Insulation in Buildings and of Building Elements, Part 1-1999 Airborne Sound Insulation’ refers to Weighted Sound Reduction Index (Rw) instead of the commonly used STC.

Resonances Frequency Hz

The frequency at which this coincidence occurs is called the critical frequency, and is a function of the particular materials used in the partition.

STC is der ived from sound transmission loss measurements over 16 test frequency bands between 125Hz and 4000Hz. Rw is calculated from frequencies ranging from 100Hz to 3150Hz. Rw is considered numerically equivalent to STC, but can vary by about 1 point.

Sound transmission loss depends heavily on the surface density (mass per square metre of surface) of a building element. For every doubling of surface density the sound transmission loss increases by about 5.6dB. This is known as the ‘Mass Law’ and is shown graphically in Figure A5.

A noise reduction of 1dB (decibel) is approximately equal to a 1 STC or 1 Rw. Note this does not apply to lower frequency sound sources. The higher the STC or Rw of a partition the more effective it will be at reducing sound transmission

Higher transmission losses than those expected by the Mass Law can be obtained by using double-leaf structures, such as stud walls. Further improvement can be achieved by using wide cavities, which is not always practical. Significant transmission loss gains are obtained by using insulation such as Bradford Rockwool or Glasswool in the cavity.

A reduction of 3dB in noise level is a noticeable improvement, and a 10dB reduction in noise level is perceived as being half as loud.

The sound transmission loss of a building element may be expressed as the decibel reduction in sound pressure level measured at the standard one-third (1/3) octave frequency bands.

Some STC examples are given below.

A more convenient means of expressing sound transmission loss is by use of a single number acoustic rating called ‘Sound Transmission Class’ (STC). This rating system is described in detail in AS1276-1979: ‘Methods for Determination of Sound Transmission Class and Noise Isolation Class of Building Partitions’. The

58

• 2 layers 16mm Gyprock each side of 64 mm steel studs

STC = 47

• As above + 75mm GW batts

STC = 57

• Double Brick Wall 250 mm

STC = 54

• Brick Wall single layer 110mm

STC = 44

• Sheet steel 0.8mm thick

STC = 27

• Aluminium window 5 mm glass

STC = 22


A C O U S T I C

D E S I G N

G U I D E

Flanking Paths.

Sound Reflection.

Noise will always take the easiest path around a barrier under question. This is known as flanking. Consider noise to be like a liquid that can pass through small openings. Flanking can severely reduce the theoretical sound transmission loss of a building element.

Sound may also be reflected from a solid surface in much the same way as a ball bounces from a wall. Reflected sound will increase the sound level on the source side of the solid. The most common example of this is a noise source such as a machine located above a hard concrete floor. Sound will radiate equally in all directions from the machine. However, sound travelling downwards will strike the floor and be reflected upwards as shown in Figure A7. The sound level above the floor will be the sum of both the direct sound and the reflected sound.

Air borne sound control is limited by flanking transmission paths which permit sound to bypass the barrier. Some of the more common flanking transmission paths are shown in Figure A6. FIG A6. COMMON FLANKING TRANSMISSIONS PATH. 1. Ceiling plenums, floors, walls. 2. Poor seals between structural elements and around service penetrations. 3. External air-borne paths.

4. Heating and ventilation ducting. 5. Rigid plumbing connections and penetrations. 6. Back-to-back cabinets and switches/power outlets.

Sound Absorption. Sound may also be absorbed by the solid. The acoustic energy is converted to heat energy as a result of frictional forces within the solid. Large amounts of sound may be absorbed with little effect on the temperature of the absorbing material. Most hard solid surfaces are highly sound reflective. Open cell or porous materials are the most effective sound absorbers. The long, narrow, twisting air paths give rise to considerable friction between vibrating air particles and the fibres or cell walls. The friction converts much of the sound energy into heat and the process is referred to as ‘sound absorption’. Increasing the thickness or density of a porous material will increase its sound absorption. Increasing the thickness is the most effective method of increasing the sound absorption of a material, particularly at the lower frequencies.

As the required performance of the wall or ceiling system increases eg. for systems over STC 45, attention to sealing of gaps to stop noise leaks is critical. Even very small gaps will derate performance significantly. Flanking can be a limiting factor in achieving the higher STC ratings for building elements in the field, especially for STC ratings greater than 55.

A material’s ability to absorb sound is expressed by its sound absorption coefficient, which is sometimes denoted by α and defined as:

STC ratings measured in the laboratory are usually higher than what is achieved in the field. Designers and specifiers of building facades need to be aware that in the field, flanking of noise at doors, windows, ventilation ducting, air gaps at ceiling, wall and floor intersections, and poor workmanship may result in lower acoustic STC performance. For these reasons CSR Bradford Insulation cannot guarantee the field STC ratings of specific construction shown in this Acoustic Design Guide and other CSR Bradford Insulation brochures.

α = 1–

(

Sound energy reflected from surface Sound energy incident on surface

)

The sound absorption coefficient is reported as a decimal, e.g. α = 0.75 would mean that 75% of the incident sound energy was absorbed while 25% was reflected. A more convenient method of describing sound absorption is to use the single number NRC (Noise Reduction Coefficient). NRC is the arithmetic average of the sound absorption coefficients at the four frequency of 250Hz, 500Hz, 1000Hz and 2000Hz. NRC is usually rounded to the nearest 0.05 as per Australian Standard AS1045 : 1988 ‘Acoustics - Measurement of Sound Absorption in a Reverberation Room’.

Maximum sound transmission loss can be achieved by eliminating penetrations in walls, caulking gaps, and staggering electrical outlet or other necessary penetrations through the wall. For optimum acoustic performance, wall cavities should be filled with either rockwool or glasswool insulation. Pipes, conduits and other outlets should have insulation tightly fitted around them.

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G U I D E

For many porous absorbers such as rockwool and glasswool, sound absorption coefficients or NRCs are commonly greater than 1.00. For example:

octave band, or more preferably for each one third octave band. The sound absorption coefficients of some typical building materials are listed in Table A3.

• 75mm thick Bradford Glasswool Supertel™ (32kg/m3) NRC = 1.09

Sound absorption coefficients may be determined in an acoustic laboratory by two different methods. The simplest of these uses a device called an ‘impedance tube’ and its use is covered by AS/NZS1935 ‘Acoustics – Determination of Sound Absorption Coefficient and Impedance in Impedance Tubes’. A more involved method uses a specifically constructed room known as a reverberation room. This method is set down in AS1045 : 1988 ‘Acoustics – Measurement Of Sound Absorption Coefficients In A Reverberation Room’.

• 50mm thick Bradford Fibertex™ 350 Rockwool (60kg/m3) NRC = 1.05 Although it is theoretically impossible to have sound absorption coefficients greater than 1, as this would mean that more sound is absorbed by the material than is incident on it, NRCs greater than 1 do occur in laboratory testing as a result of the measuring techniques and the sound field within the testing facility.

The impedance tube method being simpler, and therefore cheaper, has been favoured by some manufacturers of acoustic products. It has a major limitation however in that it only allows for normal incidence of sound as shown in Figure A8(a). In practice, sound will impinge on the sound absorbent material from all directions.

Sound absorption coefficients are measured on a linear scale and so do not relate directly to decibels. The effect of sound absorption on sound pressure level is discussed under ‘Reverberation Control’. Sound absorption materials do not absorb equal amounts of sound in all frequencies. Thus it is necessary to determine the sound absorption coefficient for each

TABLE A3. TYPICAL VALUES OF SOUND ABSORPTION COEFFICIENTS. Typical Building Materials

Frequency (Hz) 125 250 500 1000 2000 4000 Sound Absorption Coefficients (α) 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.02 0.03 0.04 0.05 0.03 0.03 0.04 0.05 0.05 0.04 0.05 0.06 0.08 0.04 0.06 0.15 0.12 0.11 0.07 0.07 0.08 0.30 0.20 0.15 0.05 0.05 0.05 0.30 0.25 0.18 0.12 0.07 0.05 0.10 0.10 0.15 0.15 0.10 0.10 0.20 0.20 0.15 0.10 0.05 0.05 0.01 0.15 0.25 0.20 0.20 0.20

Reflective Terrazzo Flooring on concrete Concrete 100mm Exposed Brick Fibrous Cement Timber Floor Plasterboard Glass window 4mm Hardboard Suspended Plasterboard Ceiling Aerated lightweight concrete Absorptive Thick Pile Carpet 0.15 0.25 0.50 0.60 Open Cell Polyurethane Foam 25mm 0.10 0.25 0.55 0.70 Polyester 25mm 0.10 0.25 0.55 0.60 Perforated Metal Pan Ceiling with Glasswool backing 0.30 0.65 0.55 0.65 ™ Bradford Flexitel Glasswool 25mm 0.10 0.33 0.66 0.90 ™ Bradford Supertel Glasswool 50mm 0.25 0.66 1.01 1.04 ™ Bradford 50mm Fibertex 350 Rockwool 0.21 0.69 1.13 1.15 Refer to Appendix C for ‘Sound Absorption Coefficients’ of Bradford Insulation products.

60

0.70 0.75 0.75 0.70 1.03 1.10 1.16

0.70 0.85 0.75 0.60 0.79 1.13 1.18

NRC 0.01 0.02 0.05 0.05 0.10 0.10 0.15 0.15 0.15 0.20 0.50 0.55 0.55 0.65 0.75 0.95 1.05


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mid to high frequencies. Low frequency absorption is influenced by the thickness of the material. The sound absorption coefficients of Bradford Rockwool and Glasswool products are shown in Appendix C of this guide.

The reverberation room allows for this random incidence as shown in Figure A8(b). For some applications such as ceilings and air conditioning ducts or glazing, glancing incidence as shown in Figure A8(c) predominates. As can easily be seen, data obtained by using normal sound incidence will be totally inappropriate for evaluating performance in glancing incidence situations.

Further improvement in low frequency sound absorption may be achieved by using Bradford Rockwool or Glasswool thicknesses greater than 50mm or by using an air space behind. For optimum acoustic absorption particularly at low frequencies, the air space should be at least as thick as the rockwool or glasswool insulation.

It is important therefore to check by which method, published sound absorption coefficients have been determined. All leading Australian manufacturers publish data measured in accordance with AS1045-1988 ‘Acoustics – Measurements of Sound Absorption in a Reverberation Room’. Some imported products may claim performance on the basis of overseas standards. Such performance data is not necessarily in accordance with the Australian standard.

The sound absorption for a surface is the product of the sound absorption coefficient and the area of the surface. The unit is the Sabin, where 1 Sabin is the amount of absorption provided by 1 square metre of surface with an absorption coefficient of 1. There is a trend to replace the Sabin with ‘equivalent absorption area’. The calculation is still the same, however units of square metres are used.

FIG A7. DIRECT AND REFLECTED SOUND.

Reverberation. When sound is produced within an enclosed space such as a room, the first sound which a listener hears is that which arrives directly from the source. The next sound to be heard will be that which has been reflected from one wall of the enclosure. After this, sound which has been reflected from two, three, or more surfaces will successively arrive.

Direct Sound

Sound Source

Re

fl

ed ect

So

und

These multiple reflected or reverberant sounds combine with each other and the direct sound to form the resulting sound field as shown in Figure A9. Not only does the reverberant sound increase the level of sound, it also increases its duration. This causes distortion of the sound with particularly detrimental effects on speech and music. When long delays occur between the arrival of direct and reflected sound, distinct echoes can be heard.

FIG A8. TYPES OF SOUND INCIDENCE.

(a)

(b)

(c)

Normal Incidence

Random Incidence

Glancing Incidence

Sound can take 2 paths in a room: the direct sound and the reflected sound. The total sound level is the sum of the direct and reflected sounds. The reflected sound will lose energy when striking the boundaries of the room. Some of this reflected sound will be transmitted and some absorbed, so that the amount of sound reflected will be less than that striking the boundary.

Sound absorption coefficients may also be calculated empirically from the flow resistivity of porous or fibrous absorbers. The flow resistivity is usually measured by an American Standard test method, ASTM C522-73, as there is no Australian Standard for this test.

For a continuous noise source, a steady-state situation will develop where the rate of sound energy entering the room from the noise source will be balanced by the rate of sound energy leaving the room by transmission and absorption.

The use of flow resistivity data enables prediction of the sound absorption coefficients for composite materials and thus minimises the number of laboratory tests required. As with all empirical calculations, predictions should be compared to actual test data to ensure the validity of the calculations. Fibrous materials such as Bradford Rockwool and Glasswool are extremely efficient absorbers of sound at 61


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TABLE A4. OPTIMUM REVERBERATION TIMES.

FIG A9. DEVELOPMENT OF REVERBERANT SOUND.

Room Acoustics Dead

Sound Source

Direct Sound =

G U I D E Reverberation Time (sec) 0.6

Hotel and airport lounges, Surgeries and consulting Rooms, Kindergarten.

Medium Dead 0.6 - 0.9

Classrooms, Restaurant, Large open-plan offices.

Medium

0.9 - 1.1

Lecture rooms, General Offices, Hospital Wards.

Medium Live

1.1 - 1.4

Board Rooms, Conference Rooms, Assembly Halls.

Reflected Sound =

REVERBERATION TIME. Reverberation Time (RT) is the time it takes a sound to travel from its source to and from reflecting surfaces and gradually become inaudible. More technically speaking, RT60 is the time taken for the reverberant sound pressure level to decrease by 60dB after the direct sound has ceased. The reverberation time of any room depends primarily upon the degree of sound reflection from the room boundaries and objects within the room. The more reflective surfaces in the room, the longer will be the reverberation time. Room dimensions also have an effect. As sound levels fall due to absorption and transmission at solid boundaries, it follows that where sound has to travel further between reflections (ie larger rooms), it will take longer for the sound pressure level to fall, resulting in longer reverberation times. Rooms used for different purposes need different reverberation times. Churches, concert halls and music studios may require reverberation times of up to 2 or 3 seconds, while for broadcasting studios and open plan offices appropriate reverberation times may be below 0.5 seconds. Reverberation time affects both the room acoustics and the noise level. Short reverberation times result in lower noise levels and what is commonly called ‘dead’ acoustics, while long reverberation times result in higher noise level, or ‘live’ acoustics. For everyday purposes, reverberation time criteria can be classified as shown in Table A4. The optimum reverberation time depends upon the intended use of the room.

Typical Example

Live

1.4

Music Rooms, Concert Halls.

Figure A10 from Australian Standard AS2107 : 1987 shows optimum reverberation times for various rooms. Reverberation times are usually quoted for frequency of 500Hz or 1kHz. Ideally, the reverberation time at higher frequencies should be the same as that at 500Hz, but in practice some reduction in reverberation time at frequencies above 2000Hz is almost inevitable. For good music listening condition the reverberations time at frequencies below 500Hz should increase while for speech there should be little deviation from the value at 500Hz.

REVERBERATION CONTROL. Increasing the amount of sound absorption within a room reduces both the reverberant sound pressure level and the reverberation time. The effect on reverberant sound pressure level is a 3dB reduction for each doubling of absorption. Thus, in a highly reflective room the addition of small amounts of sound absorbing materials will have a marked effect on the sound pressure level, while in a highly absorptive room the addition of large amounts of sound absorbing materials may have little effect. Reverberation control as a means of noise control is limited by two factors. Firstly, it is not possible to reduce the total sound pressure level below that due to direct air borne sound transmission from source to receiver. Secondly, very large amounts of sound absorption may make the room unacceptably ‘dead’ by reducing the reverberation time too much. The reverberation time depends on the room volume and the total sound absorption present in the room. It may be calculated by:

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FIG A10. MEAN REVERBERATION TIMES (FROM AS2107 : 1987).

Midfrequency Reverberation Time (sec)

3.0

2.0 s

he

c ur

h

C

ls

t er

al

H

c

on

os

nd

C

i

ud

c si

es

us

o aH er

a

Op

St

u

M

itor

1.0

ch Spee

s

Studio

r ie Va

t

n yE

te

rt

m ain

en

s

ium

c

ee

Sp

0.7

ud hA

t

e Th

at

re

s

s

dio

Film

V dT

Stu

an

0 50

100

500

1000

10000

100000

Room Volume (m3)

Note: Equation Nº5 shows that doubling the amount of absorption in the room halves the reverberation time.

Equation Nº5 T =

0.162 V A

For highly sound absorbent rooms such as recording studios, the reverberation time is more correctly calculated by:

Where: T = reverberation time (sec)

Equation Nº6

V = room volume (m3) A = Sα total absorption (Sabins)

T =

Where: S = room surface area (m2) α = average sound absorption coefficient for room surfaces

0.162 V – S ln (1 – α)

The use of CSR Bradford Rockwool or Glasswool insulation is the most effective means of absorbing sound and reducing overall sound levels in enclosed areas.

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Room Acoustics.

REVERBERATION CONTROL IN BUILDINGS. Hard surfaces are excellent reflectors of sound which magnifies the effect of the initial noise source. Where the overall noise level depends mainly on a build-up of reflected sound within the room, a significant reduction in noise level may be achieved by increasing the total sound absorption in the room. This may be achieved most simply by using absorptive rather than reflective materials at room boundaries. Increasing the sound absorption within a room will also reduce its reverberation time. In most cases this will be desirable as a high level of reflected noise generally indicates excessive reverberation time. The reverberation time should not be shortened too much as it would make the room unnaturally ‘dead’ for the purpose for which it is used. However if the space contains unwanted noise, maximum absorption is desirable.

While legislation sets noise limits for industrial exposure, it is left to the architect or consultant to set appropriate noise levels for rooms. The Standards Association of Australia provides a comprehensive list of recommendations in AS2107 : 1987 ‘Acoustics - Recommended Design Sound Levels and Reverberation Times for Building Interiors’. A guide to suitable background sound levels is given in Table A5.

TABLE A5. RECOMMEND MAXIMUM BACKGROUND NOISE LEVELS. Recommended Ambient Sound Level dB(A)

Board and conference rooms

30-35

Computer rooms

45-55

General office areas

40-45

Private offices

35-40

Small retail stores

45-50

Supermarkets

50-55

Hotel lounges

45-55

Libraries - reading areas

40-45

Restaurants

40-45

Airport lounges

45-60

Places of worship

30-35

Court rooms

25-30

Surgery and consulting rooms

40-45

Hospital wards

30-40

Classrooms

35-40

Laboratories - Teaching

35-40

Laboratories - Working

40-50

Lecture theatres - up to 250 seats

30-35

FIG A11. SOUND ABSORPTION OF DIFFERENT TYPES OF ABSORBERS. 1.4

1.2 Sound Absorption Coefficient (α)

Type of Activity

50-55

Squash courts

50-55

1.0 Dissipative Absorber 0.8

0.6

0.4 Membrane Absorber

0.2 Cavity Absorber 63

125

250 500 1000 Frequency (Hz)

2000

4000

8000

Absorbing or controlling noise within a space can be done using materials called ‘sound absorbers’ which can be grouped into 3 categories; porous or dissipative absorbers, membrane or panel absorbers and cavity absorbers (see Figure A11).

Lecture theatres - more than 250 seats 25-30 Bowling alleys

G U I D E

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POROUS OR DISSIPATIVE ABSORBERS. Porous or dissipative absorbers, (eg. rockwool or glasswool insulation) which work by converting sound energy from the moving air particles into heat through friction. This occurs in the material’s many tiny narrow fibrous airways. The thicker and denser the porous absorber is, the better the sound absorption. (Refer to Figure A12). Porous absorbers are often faced for support and/or decorated with:

G U I D E

FIG A13. BROAD-BAND SOUND ABSORBER. Plan View. Chicken Wire

Wall

Bradford Glasswool or Fibertex Rockwool

• Perforated facings - foil, metals (such as Bradford Acousticlad), timber or plasterboard. • Bradford Ultraphon™,

Airspace should be at least the thickness of the cavity insulation

Gyprock plasterboard, perforated hardboard, expanded metal or Bradford Thermofoil HD Perforated

Timber Framing

FIG A14. TIMBER PANELLING FOR LOW FREQUENCY ABSORPTION. Plan View.

• Black tissue facing, • Thin polyester film or • Fabrics.

Wall

80

ess

40

6mm

0.4

60 Thickn

0.6

0.2

Bradford Glasswool Building Blanket or Fibertex Rockwool

20

0

0 125

250

500

1000

2000

4000

Timber Panelling

Timber Batten

CAVITY ABSORBERS. Cavity absorbers are usually an enclosed volume of air with a small neck opening. The moving air particles produce a type of pumping action in the neck of the cavity, converting the sound energy into heat. Most common type of cavity absorber is a Helmholtz resonator. Cavity absorbers provide a very narrow band of sound absorption, which can be expanded with the use of rockwool or glasswool insulation in the enclosed space. These absorbers have specialised acoustic applications such as studios and auditoria and for pure tone absorption. The excellent sound absorbing properties of Bradford Rockwool and Glasswool can be used to great advantage in reverberation control.

Absorption (%)

0.8

12m mT hick ness

100

25m mT hick nes s

1.0

50mm Thick ness

Random Incidence Absorption Coefficient (x)

FIG A12. POROUS ABSORBERS – EFFECT OF THICKNESS.

8000

Freqencey (Hz)

REVERBERATION CONTROL IN BUILDINGS. Some typical examples include:

MEMBRANE OR PANEL ABSORBERS. Sound is transferred into vibrational energy in the face of the panel with maximum absorption occurring at the resonant frequency of the panel (see Figure A13). The resonant frequency is affected by surface density of the panel, the size and stiffness of the airspace behind the panel and the spacing of the panel supports. As the airspace or mass of the panel are increased, the frequency of maximum absorption, (ie. the resonant frequency) decreases. Adding rockwool or glasswool insulation in the air cavity of panel absorbers, increase their absorptive frequency range. Typical examples are solid, reflective panels (timber, plasterboard etc.) panel on studwork, lightweight partitions on studwork, suspended ceilings and windows.

UNDER-ROOF. Where condensation protection is required, install Bradford Anticon™ or Acousticon™ with foil facing under the steel roof. For better acoustic absorption, install 50mm to 100mm Bradford Fibertex™ Rockwool or Bradford Glasswool (Flexitel™, Supertel™ or Ultratel™) blanket faced with CSR Bradford Thermoplast™ 980 perforated foil. This is an effective way to add significant sound absorptive insulation.

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SUSPENDED BAFFLES. An alternative treatment which maximises absorptive area is to install Bradford Rockwool Acoustic Baffles. Baffles may be installed at any height and do not need to be all in the same plane. A regular pattern is most easily installed using a suspended ceiling grid. Inverted aluminium U-channels are fixed to the underside of the grid. The baffles are then secured to the U-channel using self tapping screws. Alternatively, individual baffles may be suspended using galvanised wire and ‘S’ hooks.

FIG A15. ABSORPTIVE WALL TREATMENT IN SCHOOL HALL. Black Matt Faced FIBERTEX™ Retained Behind Spaced Timber Strips.

WALLS. Sound absorbing walls may be constructed by retaining rockwool or glasswool behind spaced timber panels as shown in Figure A15. Alternative treatments include fixing the sound absorbing batts behind perforated plywood, perforated Gyprock® plasterboard or metal. The use of a black matt tissue finish or Bradford Ultraphon™ on the batts is recommended for aesthetic reasons. Sound absorbing panels may also be fixed to walls as shown in Figure A17. The decorative facing chosen should be acoustically transparent (with low flow resistance) to maximise the amount of sound reaching the insulation behind. Open weave fabrics are suitable for these applications.

CEILINGS. The use of black-faced Bradford Glasswool Blanket as an acoustic overlay for slatted timber, metal strip, and perforated metal pan ceilings is illustrated in Figure A15. The non-reflective black finish significantly enhances the appearance of these ceilings while the glasswool absorbs noise that would otherwise be reflected back into the room. An alternative approach is to use a fully exposed metal suspension grid to support the ceiling which also achieves an air gap behind the batts to boost low frequency sound absorption.

FIG A17. ABSORPTIVE WALL PANELLING RIGID BOARD WITH DECORATIVE FACING.

FIG A16. SOUND ABSORPTIVE TREATMENT OF METAL PAN CEILING.

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TABLE A6. INSULATION FOR NOISE REVERBERATION CONTROL. Application

Product

Comment

Sports/Community Centre Walls/Roof.

Bradford Glasswool Blanket faced with Thermoplast™ 980 Perforated Foil.

Cost effect way to add large quantity of absorption.

Insulation over Perforated Plasterboard or Perforated Metal.

Bradford Glasswool Blanket BMF or Flexitel™ BMF/Ultraphon™ .

High absorption capacity enhanced by air space behind ceiling.

Absorption Behind Cinema Screens.

Bradford Supertel™ BMF/Ultraphon™

Optimum sound absorption over all frequencies.

Cinema Wall.

Bradford Supertel™ or Ultratel™ Front Runner faced.

Absorptive and aesthetic facing.

Bottling/Canner Plant.

Bradford Acoustic Baffles.

Convenient way to add absorption to reverberant areas where conventional methods are not available.

Acoustic Enclosure.

Bradford Acousticlad™ (Fibertex™ 350 + Perforated Metal).

For industrial noise control Fibertex™ Rockwool products are excellent acoustic absorbers.

Sound Recording Studio.

Bradford Fibertex™ 350 Rockwool BMF or Ultraphon™ faced or Bradford Glasswool Ultratel™

For high level of sound absorption at low frequencies, use 100mm thickness.

Conference Room.

Bradford Ductel™ faced . with front runner

High absorption with compression resistance and aesthetic surface.

BMF = Black Matt Facing

Some of the many means by which noise can be controlled will be discussed in this brochure.

Industrial Acoustic Design Criteria.

The costs of noise control may appear high, especially when correcting existing problems, but the costs of workers compensation, non-compliance with legislation, and industrial disharmony, in the long term, can be much more expensive. The fatiguing aspects of noise may lead to lowered productivity and the cost of this in an ongoing situation is also high.

Industrial noise is a by-product of the mechanical age. Its nuisance value has long been tolerated as an unavoidable consequence of labour-saving plant and equipment. But we now know that excessive noise is not just annoying - it is also dangerous. It causes both temporary and permanent hearing damage, body fatigue, nervous stress, and adversely affects workplace safety by masking communication and warning signals. Hearing loss cannot be cured.

NOISE LEVELS. The first criterion considered here is usually noise legislation. There are essentially two components: (i) the noise level to which employees may be exposed, i.e. Occupational Noise. (ii) the noise level that the factory may emit to the surrounding community. In Australia The NSW ‘Occupational Health & Safety Regulation 1996’ (effective 31 May 1997) states ‘a place of work is unsafe and a risk to health if any person is exposed to noise levels’:

It is now generally accepted that continued exposure to noise levels of 80dB(A) or more will result in hearing loss. Already researchers are suggesting the danger level may be even lower. The increasing number of people suffering from noise induced hearing loss underlines the importance of controlling noise in factories. Noise levels can be reduced and excessive noise should no longer be considered an ‘occupational hazard’. 67


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a) that exceed an 8 hour noise level equivalent of 85dB(A) or

G U I D E

CONCENTRATION. High noise levels are known to affect concentration which leads to increased errors in machine operation and failure to detect quality defects in product. Lack of concentration can also be a safety hazard resulting in injury to employees and equipment damage. Each situation will have its own peculiarities so it is not possible to set a universal permissible noise level for all factories. Consideration of the above factors, together with the costs involved, should permit a responsible target noise level to be set.

b) ‘Peak’ noise levels of 140dB (Lin) or more. For every 3dB(A) above 85dB(A), the exposure time is halved, so that four hours exposure would be permitted at 88dB(A) and two hours at 91dB(A) and so on. Conversely, every 3dB(A) lowering of the noise levels doubles the time for which employees may be exposed. Therefore 16 hours of exposure would permitted at 82dB(A). Compliance with noise legislation does not therefore automatically ensure that employees will not suffer noise induced hearing loss.

Speech Privacy.

Permitted noise emission levels depend upon the location of the factor y and it’s proximity to residences/offices nearby. The Environment Protection Authority (EPA) sets noise criteria for noise emissions from industry.

The need to preserve confidentiality of conversation arises in many situations. Discussions in conference rooms and executive offices should not be overheard. People waiting in airport lounges or hotel lobbies wish to converse freely. Intimate diners do not wish to share their conversation with others in the restaurant. Acoustical privacy is paramount in residential situations where walls or floors abut adjoining residences. Bedrooms in one residence need to be acoustically isolated from rooms in other residences to avoid annoyance. Similarly impact noise on hard floors can irritate people in rooms below.

The character of the noise is also important. High frequency sounds are more annoying than sounds of low frequency, while noise with prominent tonal components is more annoying than broad band noise of the same intensity. The hours of operation also affect the permitted noise emission levels. Lower levels apply at night than during the day. Other aspects affected by noise level include:

The level of speech privacy required will depend on the particular situation. Three categories may be considered:

SPEECH INTELLIGIBILITY. High noise levels above 70dB(A) can make verbal communication extremely difficult and loss of speech intelligibility can occur. This leads to misunderstandings which can result in inefficient process operations, product losses, unsafe working practices, and industrial unrest.

1. Partial coherence – small portions of the conversation may be intelligible to an uninvolved listener, but he/she will not be able to follow the conversation as a whole, 2. Incoherent – an uninvolved listener can hear the sound of conversation but it is not intelligible,

MACHINE OPERATION. The sounds emitted by many machines convey important information to operators on the functioning of the machine. Excessive background noise may mask these sounds, preventing early detection of machine malfunction. Expensive repairs and loss of productivity may result.

3. Inaudibility – no sound whatever can be heard by an uninvolved listener. Speech privacy is a two-way consideration. It may be required to protect the confidentiality of conversation (eg. a boardroom meeting) or on the other hand, to avoid distraction of uninvolved listeners (eg. office workers or people in a library). Typically in commercial applications, noises such as conversations, telephones ringing etc can be heard from one office to another (also known as ‘crosstalk’). This can cause disruption, annoyance, and decreased productivity. Crosstalk usually occurs from sound flanking via the: • light weight ceilings (refer to ‘Ceilings’, page 18 for diagrams showing installation ). • Air conditioning ducts (refer to ‘Air Conditioning Noise Control’, page 36). • Windows and doors.

WARNING SIGNALS. Many warning signals or alarms rely on sound to attract people’s attention. Most alarms now incorporate both visual (e.g. flashing lights) and audio signals, but it is important to note that visual signals are only effective for the line of sight, while audio signals are designed to attract attention regardless of where an employee may be looking. High background noise levels may mask these warning signals, resulting in unsafe work practices and inefficient process operation.

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APPENDIX B.

Floor/Ceiling Systems. TABLE B1. FIRE AND ACOUSTIC CEILING SYSTEMS UTILISING CSR BRADFORD INSULATION AND CSR GYPROCK PLASTERBOARD. Detailed information on these and alternative CSR Fire and/or Acoustic Rated Ceiling Systems and Wall Systems is published in the CSR Gyprock Fire and Acoustic Design Guide, NºGYP500. Framing Method

System Nº

Fire Resistance Level FRL

Weighted Sound Rw

CSR 800

–/–/–

27

–

CSR 801

–/–/–

38

–

CSR 802 CSR 805 CSR 806 CSR 809 CSR 807 CSR 808 CSR 811 CSR 815 CSR 816 CSR 819 CSR 817 CSR 818

Impact BRADFORD Insulation Material Insulation GYPROCK® Plasterboard Ceiling Lining Class

–/–/–

42

–

30/30/30 + BCA FPC 60/60/60 + RISF 30 60/60/60 + RISF 60 90/90/90 + RISF 60 120/120/120 + RISF 60

36

–

44

–

48

–

48

–

47

–

–/–/–

44

–

46

–

47

–

50

–

52

–

55

–


No insulation No plasterboard R2.0 Bradford GOLD BATTS 1 x 13mm GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS 2 x 13mm GYPROCK Plasterboard CD No insulation 1 x 13mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 13mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 3 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1 x 13mm GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS 1 x 13mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 3 x 16mm Gyprock FYRCHEK Plasterboard

R2.0 Bradford GOLD BATTS 1 x 13 GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS CSR 823 –/–/– 53 67 1 x 10 SOUNDCHEK Plasterboard R2.0 Bradford GOLD BATTS CSR 824 –/–/– 57 70 2 x 10 SOUNDCHEK Plasterboard R1.5 Bradford GOLD BATTS 30/30/30 CSR 825 53 – 56 48 – 67 1 x 13mm Gyprock FYRCHEK Plasterboard + BCA FPC R1.5 Bradford GOLD BATTS 60/60/60 CSR 826 54 49 – 68 1 x 16mm Gyprock FYRCHEK Plasterboard + RISF 30 R1.5 Bradford GOLD BATTS 60/60/60 CSR 829 57 50 – 70 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard + RISF 60 R1.5 Bradford GOLD BATTS 90/90/90 CSR 827 57 51 – 70 2 x 16mm Gyprock FYRCHEK Plasterboard + RISF 60 RISF = Resistance to Incipient Spread of Fire. BCA FPC = Building Code of Australia Fire Protective Covering. CSR 821

–/–/–

53

69

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TABLE B1. (continued) Framing Method

System Nº

Fire Resistance Level FRL

Weighted Sound Rw

CSR 831

–/–/–

48

–

CSR 833

–/–/–

48

–

CSR 832

–/–/–

53

–

CSR 834

–/–/–

53

–


48

–

51

–

55

–

55

–

58

–

–/–/–

54

67


54

67

58

70

62

70

62

73

62

75

CSR 860

–/–/–

50

–

R1.5 Bradford Glasswool ANTICON over purlins 1 x 13mm GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS on ceiling

CSR 865

90/90/90 + RISF 60

49

–

R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard

CSR 870

60/60/60 + RISF 60

44

–

R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard

CSR 871

90/90/90 + RISF 60

44

–


CSR 875

60/60/60 + RISF 60

49

–

R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard

CSR 876

90/90/90 + RISF 60

49

–


CSR 835 CSR 836 CSR 839 CSR 837 CSR 838

CSR 841 CSR 845 CSR 846 CSR 849 CSR 847 CSR 848

Impact BRADFORD Insulation Material Insulation GYPROCK® Plasterboard Ceiling Lining Class

R2.0 Bradford GOLD BATTS 1 x 13 GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS 1 x 10 SOUNDCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 13 GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS 2 x 10 SOUNDCHEK Plasterboard R2.0 Bradford GOLD BATTS 1 x 13mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 3 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1 x 13mm GYPROCK Plasterboard CD R2.0 Bradford GOLD BATTS 1 x 13mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 1x13mm+1x16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 2 x 16mm Gyprock FYRCHEK Plasterboard R2.0 Bradford GOLD BATTS 3 x 16mm Gyprock FYRCHEK Plasterboard

RISF = Resistance to Incipient Spread of Fire. BCA FPC = Building Code of Australia Fire Protective Covering.

NOTE: Bradford FIBERTEX™ Rockwool Batts. When using Bradford FIBERTEX™ Rockwool Batts in the systems detailed in Table B1, Rw or STC rating is generally increased by 1 to 3 units. Please refer to the CSR Bradford Insulation Acoustic Design Guide or contact your regional CSR Bradford Insulation office for more information.

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APPENDIX C. CSR BRADFORD INSULATION PRODUCT DATA.

Bradford Acoustilag. ™

CSR Bradford Insulation offers three types of Acoustilag™: Acoustilag™ 20, Acoustilag™ 23 and Acoustilag™ 26

TABLE C1. BRADFORD ACOUSTILAG SPECIFICATIONS. Product

SoundLagg™ Mass (kg)

Insulation Thickness (mm)

Standard Roll Size

Noise Reduction dB(A)*

Bradford ACOUSTILAG™ 20

3.0

25

5m x 1200mm

20dB(A)


4.5

50

5m x 1200mm

23dB(A)


8

50

3m x 1200mm

26dB(A)

* ‘Noise Reduction’ refers to Insertion Loss which is the difference between the sum of the A-weighted Sound Power Levels of the lagged and unlagged pipes. The Acoustilag Noise Reductions of 20 23 and 26dB(A) ONLY apply to water flowing through PVC pipes.

Table C2 details CSR Bradford’s Acoustilag systems using CSR Gyprock® plasterboard to achieve the strict STC noise requirements specified by the BCA (Building Code of Australia). TABLE C2. BRADFORD ACOUSTILAG™ SYSTEMS. System

STC

Bradford Acoustilag

CSR Gyprock® Plasterboard

Bradford Insulation

BAS 01

STC 30

ACOUSTILAG™ 20

1 layer 10mm CSR Gyprock® Plasterboard

-

ACOUSTILAG™ 20

2 layers 13mm CSR Gyprock® Plasterboard


ACOUSTILAG™ 23



ACOUSTILAG™ 23


105mm Bradford Glasswool, R2.0

ACOUSTILAG™ 26



BAS 02

STC 45

BAS 03 BAS 04 BAS 05

STC 50

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TABLE C3. BRADFORD ACOUSTILAG™ INSERTION LOSSES. Product 125*

Sound Insertion Loss (Octave Band Centre Frequency HZ) 250* 500* 1000* 2000* 4000*

Insertion Loss 8000* Overall*

ACOUSTILAG™ 20

4

-1

4

14

21

30

29

20

ACOUSTILAG™ 23

1

-4

8

17

27

42

50

23

ACOUSTILAG™ 26

3

-2

10

20

29

43

50

26

* Sound Insertion Loss is the difference in sound power levels of a bare (unlagged) pipe versus the lagged (insulated) pipe in 1/3 octave bands from 100Hz to 10kHz. Noise source: water flowing through PVC pipes. National Acoustic Laboratories (NAL) test reports are available on request.

FIG C1. BRADFORD ACOUSTILAG™ INSERTION LOSSES. 60

50

30

Bare Pipe

20

AcoustilagTM 20 AcoustilagTM 23

10

AcoustilagTM 26

0

10000

8000

6300

5000

4000

3150

2500

2000

1600

1250

1000

800

630

500

400

315

250

200

160

125

-10 100

Souond Power Levels (dB) re: 1 pW

40

Frequency (Hz)

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Bradford Acousticlad. ™

TABLE C4. ACOUSTICLAD™ TEST CONFIGURATIONS AND ACOUSTIC TEST RESULTS. All five Bradford Acousticlad™ samples tested and detailed in Tables C4 and C5 use perforated aluminium panel with Bradford 50mm thick Fibertex™ 350 Rockwool -(60kg/m3) Insulation. Test Report Number ATF 771

Acousticlad Perforated % Open Area 15%

ATF 772 ATF 773 ATF 774

25% 40% 15%

ATF 775

15%

Test Sample Configuration

Noise Reduction Coefficient NRC

(60kg/m3) Insulation with black matt tissue between the rockwool and Acousticlad™ face. NRC 1.00 as above NRC 0.95 as above NRC 1.00 23µmm thick Mylar film between unfaced Bradford Fibertex™ 350 Rockwool and Acousticlad™ perforated aluminium. NRC 0.90 ™ 50mm thick Bradford Fibertex 350 Rockwool Insulation with black matt tissue between the rockwool and perforated aluminium. Timber spacers supporting panels with average air gap 30mm. NRC 1.05

Note: – All acoustic tests in Table above conducted with Acousticlad™ perforated aluminium panels (0.7mm thick), with Bradford 50mm thick Fibertex™ 350 Rockwool (60kg/m3) insulation. – Acoustic tests (ATF 771-775) were conducted in reverberation room at the National Acoustic Laboratories, Chatswood, Sydney, Australia.

TABLE C5. ACOUSTICLAD™ ABSORPTION COEFFICIENTS IN 1/3 OCTAVE BANDS. NAL Test Report Number ATF 771 Frequency Acoustical Hz Absorption 100 0.20 125 0.30 160 0.45 200 0.70 250 0.85 315 1.00 400 1.05 500 1.05 630 1.05 800 1.05 1000 1.00 1250 1.00 1600 1.00 2000 1.00 2500 0.95 3150 1.00 4000 1.00 5000 0.90 Noise Reduction Coefficient (NRC) 1.00

ATF 772 Acoustical Absorption 0.25 0.25 0.45 0.70 0.80 0.90 1.05 1.05 1.00 1.10 1.00 1.00 0.95 1.00 1.00 1.00 0.95 0.95 0.95 73

ATF 773 Acoustical Absorption 0.20 0.30 0.45 0.70 0.80 1.00 1.00 1.10 1.05 1.00 1.00 1.00 1.00 1.00 1.00 1.05 1.00 0.95 1.00




A C O U S T I C

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Sound Absorption Coefficients. TABLE C6. NOISE REDUCTION COEFFICIENTS BRADFORD ROCKWOOL PRODUCTS. Bradford Insulation Rockwool products exhibit the following sound absorption coefficients when tested in accordance with AS1045 - 1988, Reverberation Room Method. Product Bradford Rockwool Ceiling Batts R 2.0 R 2.5 Bradford Rockwool Building Blanket R1.2 R1.2 R1.2 Bradford Rockwool Wall & Floor Batts R1.5 R 2.0 Bradford Rockwool FIBERTEX™ 350 R-rated Ductliner

Facing

Frequency (Hz)

mm

125

250

500

1000 2000 4000 5000

Nil

80 100

0.57 0.75

1.00 1.20

1.20 1.19

1.06 1.07

1.11 1.10

1.11 1.09

1.10 1.10

1.10 1.15

Nil BMF THERMOFOIL™ HD Perf.

50 50

0.24 0.30

0.73 0.75

0.93 0.90

1.10 0.95

1.12 0.95

1.12 1.00

1.14 1.00

0.96 0.90

50

0.20

0.80

1.00

1.00

1.00

0.95

0.85

0.95

Nil

75 95

0.22 0.57

0.49 1.00

0.96 1.20

0.96 1.06

1.02 1.11

1.08 1.11

1.09 1.10

0.85 1.10

Nil

25 50

0.18 0.21

0.29 0.69

0.69 1.13

0.86 1.15

1.05 1.16

1.20 1.18

1.16 1.14

0.72 1.03

25 50 25 50

0.14 0.31 0.15 0.36

0.38 0.83 0.33 0.76

0.87 1.16 0.74 1.19

1.07 0.99 0.94 1.09

1.06 0.90 1.03 1.03

0.90 0.78 1.04 1.04

0.79 0.73 0.98 0.90

0.85 0.97 0.76 1.01

25 50

0.11 0.29

0.20 0.76

0.80 1.07

1.10 1.10

10.2 1.09

1.12 1.07

1.20 1.09

0.77 1.01

25 50 50 50

0.12 0.27 0.43 0.54

0.27 0.78 0.99 0.99

0.80 1.23 1.09 1.07

1.17 1.17 1.11 0.81

1.16 1.13 1.04 0.57

0.80 1.00 1.03 0.33

0.86 0.94 1.03 0.25

0.85 1.08 1.06 0.85

THERMOFOIL™ HD Perf. BMF Bradford Rockwool FIBERTEX™ 450

Thickness

Nil THERMOFOIL™ HD Perf. ULTRAPHON™ ACOUSTITUFF™

NRC*

Bradford Rockwool FIBERTEX™ 650

Nil

25 50

0.21 0.59

0.29 0.97

0.52 1.18

1.14 1.00

1.02 1.04

0.97 1.02

1.06 1.03

0.74 1.05

Bradford Rockwool Acoustic Baffle

Mylar

50

0.17

0.41

0.87

1.22

1.12

0.95

0.90

0.91

* NRC: Arithmetic average of absorption coefficients of frequency 250Hz, 500Hz, 1000Hz and 2000Hz.

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TABLE C7. NOISE REDUCTION COEFFICIENTS BRADFORD GLASSWOOL PRODUCTS. Bradford Insulation Glasswool products exhibit the following sound absorption coefficients when tested in accordance with AS1045 : 1988, Reverberation Room Method. Product

Facing

R-Value

Frequency (Hz)

(Thickness)

125

250

500

1000 2000 4000 5000

Nil (105mm)

R 2.0

0.60

0.98

1.03

1.05

1.14

1.10

1.09

1.05

Nil

R2.0 (95mm)

0.57

0.78

0.97

0.91

0.96

1.00

0.95

0.91

THERMOFOIL™ R 1.5 LD Plain (55 mm)

0.34

0.86

1.04

0.41

0.20

0.07

0.04

0.66


0.60

1.21

0.90

0.41

0.28

0.10

0.12

0.70

0.72

1.43

0.82

0.43

0.26

0.14

0.08

0.75

`

THERMOFOIL™ R2.5 LD Plain (95 mm)

Bradford Glasswool ACOUSTICON™


0.14

1.02

0.82

0.42

0.38

0.29

0.38

0.66

Bradford Glasswool GOLD BATTS™ for Ceilings Bradford Glasswool Gold Batts for Walls & Floors Bradford Glasswool ANTICON™ Roofing Blanket

Bradford Glasswool Building Blanket

NRC*

Nil

R1.2 (50 mm)

0.25

0.65

0.80

0.90

0.90

1.00

1.05

0.80

Nil

R1.8 (75 mm)

0.35

0.80

0.85

0.90

0.90

1.10

1.05

0.85

THERMOFOIL™ R1.2 HD Perf (50mm)

0.30

0.65

0.90

1.00

0.90

0.85

0.85

0.86

0.35

0.75

1.00

1.10

0.95

0.85

0.85

0.95

THERMOFOIL™ R1.8 HD Perf (75 mm) BMF

50 mm

0.25

0.70

0.80

0.95

0.90

0.95

1.05

0.84

BMF

75mm

0.35

0.75

0.85

0.85

0.90

1.00

1.05

0.86

Bradford Glasswool Ceiling Panel Overlays

Nil

50 mm

0.34

0.86

1.04

0.41

0.20

0.07

0.04

0.65

Bradford Glasswool MULTITEL™ 18kg/m3

Nil

25

0.12

0.74

1.07

0.52

0.26

0.14

0.08

0.65

Bradford Glasswool FLEXITEL™ 24kg/m3

THERMOFOIL™ HD Perf.

25 50

0.10 0.39

0.33 0.84

0.66 1.08

0.90 1.20

1.03 1.06

0.79 1.01

0.76 0.95

0.75 1.05

BMF

25 50

0.09 0.27

0.33 0.69

0.57 1.08

0.73 1.06

0.90 1.11

0.99 1.10

1.01 1.09

0.65 1.00


NOTE: Data included in this Acoustic Design Guide may be used as a guide for design purposes. However, CSR Bradford Insulation recommends that an acoustic consultant be referenced for critical design applications, or where interpolation of data may be required. Acoustic testing is subject to variation from laboratory to laboratory. 75


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TABLE C7. (continued) NOISE REDUCTION COEFFICIENTS BRADFORD GLASSWOOL PRODUCTS. Bradford Insulation Glasswool products exhibit the following sound absorption coefficients when tested in accordance with AS1045 : 1988, Reverberation Room Method. Product

Facing

Thickness

Frequency (Hz)

mm

125

250

500

1000 2000 4000 5000

Nil

25 50 75

0.12 0.27 0.52

0.41 0.75 0.94

0.63 1.12 1.24

0.90 1.12 1.13

1.01 1.07 1.06

0.99 1.04 1.09

0.94 1.03 1.02

0.74 1.01 1.09

THERMOFOIL™ HD Plain

25 50

0.12 0.46

0.56 1.10

1.18 0.92

0.53 0.46

0.17 0.19

0.10 0.09

0.12 0.06

0.60 0.65


25 30 50 75

0.08 0.12 0.23 0.52

0.39 0.48 0.71 1.02

0.73 0.84 0.99 1.15

1.02 0.86 1.09 1.07

1.12 0.87 0.97 1.02

0.84 0.94 0.78 0.90

0.75 0.87 0.59 0.83

0.81 0.81 0.94 1.06

BMF

13 25 50

0.09 0.07 0.24

0.14 0.26 0.62

0.29 0.65 1.00

0.56 0.93 1.07

0.72 1.04 1.12

0.87 1.03 1.15

0.90 1.00 1.17

0.40 0.72 0.95

THERMOFOIL HD Perf + Mylar™ film 50

0.32

1.14

0.94

0.48

0.22

0.06

0.03

0.70

Bradford Glasswool SUPERTEL™ 32 kg/m3/ Ductliner

NRC*

Perforated Metal

25 50

0.13 0.31

0.32 0.74

0.59 1.00

0.83 1.09

0.99 1.06

0.97 1.03

0.94 0.98

0.68 0.95

ULTRAPHON™

25 30 50

0.10 0.13 0.30

0.39 0.52 1.01

0.79 0.97 1.31

1.00 1.08 1.20

1.05 0.96 1.05

1.00 0.90 0.97

0.95 0.90 0.95

0.81 0.88 1.14

ACOUSTITUFF™

25 30 50

0.14 0.16 0.33

0.45 0.46 1.01

0.99 0.86 1.17

0.97 0.95 0.99

0.55 0.45 0.64

0.29 0.25 0.34

0.25 0.18 0.28

0.75 0.71 0.95

Nil

25 50

0.03 0.34

0.24 0.65

0.65 1.23

0.98 1.11

1.07 1.08

1.03 1.02

1.01 0.98

0.74 1.02


25 75

0.12 0.69

0.31 1.19

0.81 1.15

1.09 1.09

1.09 1.03

0.91 0.92

0.89 0.90

0.83 1.12

BMF

25 50

0.08 0.25

0.30 0.70

0.71 1.13

0.99 1.13

1.07 1.12

1.08 1.12

1.16 1.12

0.77 1.01

ACOUSTITUFF™

25 50

0.05 0.30

0.55 0.75

0.65 0.90

0.90 0.85

0.70 0.65

0.50 0.50

0.50 0.60

0.70 0.79

Bradford Glasswool QUIETEL™ 130 kg/m3

Nil

13 25 50

0.06 0.07 0.36

0.08 0.28 0.81

0.28 0.74 1.12

0.62 1.04 1.18

0.86 1.13 1.11

1.06 1.09 1.12

1.04 1.11 1.22

0.46 0.80 1.05

Bradford Glasswool THERMATEL™ 44 kg/m3

Nil

50 75

0.42 0.51

0.74 1.10

1.10 1.18

1.12 1.08

1.08 1.02

1.00 1.03

0.97 1.07

1.00 1.09


25 50

0.06 0.35

0.38 0.91

0.93 1.15

1.10 1.12

1.10 1.08

1.00 0.93

0.87 0.85

0.88 1.06

Bradford Glasswool Premium Ductliner/ ULTRATEL™ 48kg/m3

Bradford Glasswool DUCTEL™ 80 kg/m3


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Insertion Loss Data.

TABLE C8. STATIC INSERTION LOSS OF INTERNAL DUCT LININGS. Bradford Rockwool exhibits the following when tested in accordance with Static Insertion Loss as internal duct linings AS1277 : 1983 ‘Acoustics - Measurement Procedure For Ducted Silencers’. Test Report 300610/1-97. Insertion Loss (dB loss 600x600x4000 test duct) Product Facing Thickness Octave Band Centre Frequency (Hz) mm 63 125 250 500 1000 2000 4000 Bradford Glasswool BMF 50 1.4 4.6 16.8 53.2 51.6 32.4 24.4 DUCTLINER THERMOFOIL™ 50 1.6 5.3 18.9 53.4 48.3 31.8 24.6 3 32 kg/m HD Perf. 23µm Melinex + THERMOFOIL™ 50 1.9 5.7 21.1 26.6 16.7 12.9 12.8 HD Perf. ACOUSTITUFF™ 50 2.5 4.7 21.3 46.8 39.3 23.3 17.4 ™ ULTRAPHON 50 2.0 5.0 20.9 51.5 46.6 30.3 27.5 Bradford Premium Ductliner ULTRATEL ACOUSTITUFF™ 50 – 4.9 14.2 39.0 37.0 22.4 18.6 3 48 kg/m Bradford FIBERTEX™ THERMOFOIL™ DUCTLINER HD Perf. 50 2.8 5.8 19.9 56.6 49.1 32.4 24.6 60 kg/m3 TABLE C9: INSERTION LOSS DATA FOR ULTRAPHON SILENCERS. Bradford Ultraphon™ facing exhibits the following characteristics when tested to AS1277 : 1983 ‘Acoustics Measurement Procedure For Ducted Silencers’. TABLE C9(a). Static Insertion Loss in dB of Silencer utilising two (2) modular side splitters, 150mm thick ULTRAPHON™-faced Glasswool with a single 300mm wide throat with two (2) test lengths of 1200mm and 2400mm in a 610 x 610mm test duct. Octave Band Centre Frequency (Hz) 63 125 250 500 1k 2k 4k 8k Static Insertion Loss (dB) for 1.2m

2.5

9.8

11.7

16.0

14.5

12.8

11.5

11.3

Static Insertion Loss (dB) for 2.4m

5.3

15.1

23.6

28.3

24.4

20.0

16.4

15.3

TABLE C9(b). Static Insertion Loss in dB of Silencer utilising two (2) modular side splitters, two (2) 50mm thick ULTRAPHON™-faced Glasswool and two (2) 100mm thick double-sided ULTRAPHON™-faced splitters with three (3) 100mm wide throats with two (2) test lengths of 1200mm and 1800mm in a 610 x 610mm test duct. Octave Band Centre Frequency (Hz)

63

125

250

500

1k

2k

4k

8k


1.5

4.3

17.3

35.1

45.7

33.6

31.3

33.0


2.0

6.1

19.1

40.1

53.9

42.0

32.7

27.3

TABLE C9(c). Static Insertion Loss in dB of Silencer utilising two (2) modular side splitters, 100mm thick ULTRAPHON™-faced Glasswool with a single 180mm wide throat with two (2) test lengths of 1200mm and 1800mm in a 510 x 380mm test duct. Octave Band Centre Frequency (Hz)

63

125

250

500

1k

2k

4k

8k


2.0

6.8

18.5

29.2

28.1

20.4

16.8

16.2


3.7

9.2

26.7

36.2

37.3

27.9

22.4

19.6

BRADFORD ROCKWOOL FIBERTEX 450 80kg2 TABLE C9(d). Static Insertion Loss in dB of Silencer utilising two (2) modular side splitters, 50mm thick ULTRAPHON™-faced Fibertex 450 Rockwool with a single 180mm wide throat with two (2) test lengths of 1200mm and 1800mm in a 510 x 380mm test duct. Octave Band Centre Frequency (Hz)

63

125

250

500

1k

2k

4k

8k


1.9

5.5

16.6

28.7

39.1

31.4

26.1

22.7

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Air Flow Resistivity. TABLE C10. BRADFORD ROCKWOOL AIR FLOW RESISTIVITY. The Bradford Rockwool range achieves the following Air Flow Resistivities, when tested in accordance with ASTM C522 : Method for airflow resistance of acoustical materials. Product

Air Flow Resistivity (mks Rayls/m)

Bradford Rockwool Building Blanket

13000

Bradford FIBERTEX™ 350 Rockwool

22000

Bradford FIBERTEX 450 Rockwool

33000

Bradford FIBERTEX™ 650 Rockwool

53000

Bradford FIBERTEX™ HD Rockwool

70000

™

TABLE C11. BRADFORD GLASSWOOL AIR FLOW RESISTIVITY. Bradford Insulation glasswool products achieve Air Flow Resistivities shown, when tested in accordance with ASTM C522: Method for airflow resistance of acoustical materials. Product

Air Flow Resistivity (mks Rayls/m)

Bradford Glasswool Building Blanket

5600

Bradford Glasswool MULTITEL™

15300

Bradford Glasswool FLEXITEL™

16200

Bradford Glasswool SUPERTEL™ (Plain) (Foil)

18200 23400

Bradford Glasswool ULTRATEL™ (Plain) (Foil)

31500 30300


55600

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APPENDIX D.

Terminology. ACOUSTIC. absorption coefficient (α):

The ratio of the sound absorbed by a surface to the total incident sound energy.

attenuation:

The reduction in intensity of a sound signal between two points in a transmission system.

decibel (dB):

An acoustic unit of sound level based on 10 times the logarithm to the base 10 of the ratio of two comparable sound intensities.

flanking transmission:

The transmission of sound between two points by any indirect path.

frequency:

The number of vibrations per second. The unit is the Hertz (Hz), equivalent to one complete oscillation per second.

reverberation:

The persistence of sound within a space due to repeated reflections at the boundaries.

British thermal unit (Btu): calorie (cal): capacity, thermal or heat:: conductance, thermal: surface heat transfer coefficient (f): conduction conductivity, thermal (k):

convection: dewpoint emissivity humidity, absolute: humidity, relative: Kelvin K: permeance: permeability: radiation: resistance, thermal: resistivity, thermal: specific heat: transmittance, thermal or overall heat transfer coefficient

THERMAL. Heat required to raise the temperature of 1 lb of water 1°F. Heat required to raise the temperature of 1 gram of water 1°C. Heat required to raise the temperature of a given mass of a substance by one degree This equals the mass times the specific heat in the appropriate units (metric or imperial) Time rate of heat flow per unit area between two parallel surfaces of a body under steady conditions when there is unit temperature difference between the two surfaces. Time rate of heat flow per unit area under steady conditions between a surface and air when there is unit temperature difference between them. Heat transfer from one point to another within a body without appreciable displacement of particles of the body. Time rate of heat flow per unit area and unit thickness of an homogeneous material under steady conditions when unit temperature gradient is maintained in the direction perpendicular to the area. Heat transfer from a point in a fluid by movement and dispersion of portions of the fluid. Temperature at which a sample of air with given water vapour content becomes saturated when cooled at constant pressure. Capacity of a surface to emit radiant energy; defined as the ratio of the energy emitted by the surface to that emitted by an ideal black body at the same temperature. Mass of water vapour per unit volume of air. Ratio of the partial pressure of water vapour in a given sample of air to the saturation pressure of water vapour at the same temperature. The unit of thermodynamic temperature. For the purpose of heat transfer, it is an interval of temperature equal to 1°C. Time rate of transfer of water vapour per unit area through a material when the vapour pressure difference along the transfer path is unity. Permeance for unit thickness of a material. Heat transfer through space from one body to another by electromagnetic wave motion. Reciprocal of thermal conductance, or ratio of material thickness to thermal conductivity Reciprocal of thermal conductivity. Ratio of the thermal capacity of a given mass of a substance to that of the same mass of water at 15°C. Time rate of heat flow per unit area under steady conditions from the fluid on one side of a barrier to the fluid on the other side when there is unit temperature difference between the two fluids. 79


A C O U S T I C

D E S I G N

G U I D E

Bradford Insulation CSR Building Solutions Website.

www.csr.com.au/bradford

Manufacturing Facilities. CSR Bradford Insulation is a leading insulation manufacturer in Australia and Asia with manufacturing facilities located throughout the region.

AUSTRALIA.

ASIA. Glasswool factory, Zhuhai, China. Rockwool factory, Dongguan, China. Rockwool factory, Rayong, Thailand. Rockwool factory, Kuala Lumpur, Malaysia. Flexible Duct factory, Singapore.

Glasswool factory, Ingleburn NSW. Rockwool factory, Clayton VIC. Thermofoil factory, Dandenong VIC.

Sales Offices. State Head Office NSW ACT VIC TAS QLD SA NT WA

AUSTRALIA. Phone Fax 61 2 9765 7100 61 2 9765 7029 (02) 9765 7100 (02) 9765 7052 (02) 6239 2611 (02) 6239 3305 (03) 9265 4000 (03) 9265 4011 (03) 6272 5677 (03) 6272 2387 (07) 3875 9600 (07) 3875 9699 (08) 8344 0640 (08) 8344 0644 (08) 8984 4070 (08) 8947 0034 (08) 9365 1666 (08) 9365 1656

INTERNATIONAL. Country Phone Fax New Zealand 64 9579 9059 64 9571 1017 Hong Kong 852 2754 0877 852 2758 2005 China (Glasswool) 86 756 551 1448 86 756 551 1447 China (Rockwool) 86 769 611 1401 86 769 611 2900 Thailand 66 2736 0924 66 2736 0934 Malaysia 60 3 3341 3444 60 3 3341 5779 Singapore 65 861 4722 65 862 3533

Health and Safety Information. Information on any known health risks of our products and how to handle them safely is displayed on the packaging and/or the documentation accompanying them. Additional information is listed in product Material Safety Data Sheets available from your regional CSR Bradford Insulation office or visit our website.

CSR Limited warrants its Bradford Insulation products to be free of defects in materials and manufacture. If a CSR Bradford Insulation product does not meet our standard, we will, at our option, replace or repair it, supply an equivalent product, or pay for doing one of these. This warranty excludes all other warranties and liability for damage in connection with defects in our products, other than those compulsorily imposed by legislation. CSR Bradford Insulation is a business of CSR Limited A.B.N. 90 000 001 276. CSR Limited is the owner of the following trade marks. Acousticlad™, Acousticon™, Acoustilag™, Anticon™, Bradfix™, Bradford™, Comfort Plus™, Ductel™, Fibermesh™, Fibertex™, Fireseal™, Flexitel™, Flex-skin™, Gold Batts™, Multitel™, Quietel™, SoundScreen™, Spanseal™, Specitel™, Supertel™, Thermaclad™, Thermatel™, Thermodeck™, Thermofoil™, Thermokraft™, Thermoplast™, Thermotuff™, Ultratel™.

80

BI104.BMS6884.0901

Warranty.


Acoustic Guide

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