Title: The Physics of Playing French Horn
Name: Date:
Bethany Deibler Deibler May 30, 2008
Spring quarter Class:
Physics 100
Sidibe, 9:10 WORKING TOWARD: A
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The French horn is a unique instrument. It is included in both the brass and woodwind categories of instruments. It is one of the largest instruments as a double horn is up to 24 feet long when unraveled. Another common question about the French horn is whether it is actually French or not. The British originally had a hunting horn. The French also had a horn that was similar, but larger and used typically for actual music production, not just hunting. However, these two instruments were very similar and the names for them are interchangeable. In fact, the issue about whether the horn is actually French is debated. In Europe, they are simply called horns and here in America we call them French horns. Another theory is that the horn originated in the Alps and Germanic countries for protecting flocks. These mountains were mainly populated by French people, thus the French horn. The original horn did not have any valves. The notes were far apart and harsh sounding. This is because of the original use for the horn, which was hunting. There were many different variations of the horn used for a variety of different things. Some were used in battle; others were used in protecting flocks, and still others for hunting. Since the 17 th century, the round shape has been the same. However, there have been valves added as well as more slides. Originally, before valves, a horn player had to switch out the slides of different lengths to get different pitches. This was very inconvenient for playing the horn as a musical instrument in concert. A French horn consists of four main parts; the bell, the valves, the lead pipe, and mouthpiece, as well as the slides. Each one plays an important part in making a beautiful tone. A fascinating thing to think about is the fact that these parts function the way they do because of physics. I will look at how each part works along with the physics of the instrument. As an instrumentalist, there are three qualities of sound that are of interest; pitch, loudness, and quality. All of these require using air. Air is the most important part of playing the instrument. Without air there is no sound. With a little bit of air, there is a poor sound. But with a lot of air, a good pure tone can be produced. What makes the sound?
In order to have sound, we must start with a vibration. This vibration is in the lips of the player. Sound is produced by an oscillating motion or air flow. Contrasting with random noise, a tone or musical
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note has a constant wave for motion. Noise is not a constant sound wave.
When a tuning fork is struck, sound waves are produced. Sound waves are caused by vibrations. They follow either a sine or cosine pattern. These waves are directly related to the frequency of the sound. The oscillatory motion that the air makes through the mouthpiece is similar to the movement of a pendulum swinging back and forth. The length apart of each period is directly related to the frequency. Frequency = 1/period. It is also called simple harmonic motion. The amplitude of a sine way is the distance from the midpoint to the crest of the wave. The wavelength is the distance from the top of one crest to the top of the nest. By wave motion, we can see light and hear sounds. It is energy transferred from one source to another. When the waves stop, the air particles return to their original position. Wave speed = wavelength * frequency. This relationship can be used for all types of waves. Transverse waves are sideways motions, perpendicular to the wave. The strings on stringed instruments move in transverse waves. There are also longitudinal waves. These are waves that move along the direction of the waves, not at right angles of the direction. These are sound waves. The air inside an instrument must vibrate and be at a pressure higher than the normal atmosphere to produce a sound. The bell resonates with the sound that is produced by a steady stream of air. Certain notes have certain pitches or frequencies. Frequencies are measured in Hertz after Henry Hertz. He was the first to discover radio waves in 1886. One hertz is equal to one vibration per second. A common frequency to tune instruments to is the note A which is a frequency of 440 Hz. A piano’s A key hits the A string which then vibrates 440 times per second. A note one octave below that would be 220 Hz. Humans can hear from about 10 Hz. to 20,000 Hz. or 20 KHz. Sounds less than 20 Hz are called infrasonic waves and more than 20,000 Hz are called ultrasonic waves. How does sound travel through air?
Air is a relatively poor conductor of sound. Other materials are much better for conducting sound. In fact, sound travels four times faster in water than in air and about fifteen times faster in steel than in air. In general, the speed of sound is greater in solids than in liquid and greater in liquids than in gases. The speed of sound also depends on the weather conditions. Things such as temperature, wind, and 3
humidity effect how fast sound travels. All levels of sounds travel at the same speed, no matter how loud or soft they are. In a condition where there is zero moisture in the air and 0 degrees Celsius, sound travels about 330 meters per second, which is about 1200 kilometers per hour! Moisture increases the speed of sound as well as warm air. For each degree that the temperature is raised, the speed of sound increases by 0.6 meters per second. Reflections or echoes are the reasons that we hear things. Sound reflects similarly to light. From a smooth surface, the sound will reflect off of it with the same angle that is hit the wall. When there are many reflections happening at the same time this is called reverberations. Acousticians use this when designing halls to get the best quality of sound sitting anywhere in the auditorium. Sound is also refracted by wind and temperatures. These waves get bent and travel in unnatural paths. Different speeds of sound result in refraction. If it is a warm day, the air closer to the ground will be warmer than the rest of the air. This will cause the sound waves to bend away from the ground causing an inconsistency in the direction and speed that it is traveling. Sound also travels slower at higher altitudes and goes away from the ground which is why we don’t hear thunder for storms that are far away. However, on a cold day or at night when the air next to the ground is cold, sound waves are heard much easier. Sound refraction underwater also depends on the temperature. Since the ocean is so many different temperatures in different places, this creates a lot of inconsistency. This leaves gaps and places for submarines to hide from detection. How do you make different pitches?
Different pitches on the horn are obtained either by using the valves, or changing the air speed and volume. The air that is blown through the instrument vibrates at some frequencies much easier than other frequencies. These frequencies determine the pitch that comes out of the instrument. When the player changed the length of the instrument, the pitch changes with it. With a French horn, when you push down a lever, it changes the direction of the air flow into a pipe of a different length thus changing the pitch. Larger instruments require more air, so more air is necessary to play notes with a good tone. A weak tone is caused by a weak stream of air through the instrument. Each note that can be played without pressing the valves is called a partial. There are some partials that are easier to play than others. Each partial has its own frequency for it to be in tune. This is also called a harmonic series. On a French horn, the harmonic series is fairly close together as a whole scale can almost be played without using the valves. However, the notes are not always in tune in the harmonic series. Some horns only use this harmonic series to play a piece. This is difficult and requires a
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lot of flexibility in the lips and ears to hear the tones that you want to sound. French horn is a more difficult instrument to play than trumpet because the harmonics are so close together. Often during a song, it is hard to tell which note is supposed to be played and it is easy to get on the wrong partial, a third or a fifth away from the note that is supposed to be played. Each one of the horn’s harmonic series is an odd multiple of 23Hz. These are: 23Hz, 69Hz, 115Hz, 161Hz, and more. The equation to come up with these numbers is given by f = nv/4L. Where n is an odd number, the frequency equals n times the speed of sound divided by 4 times the length of the wave. These are all the notes that can be played without using the valves.
Horn harmonic series. Horn players are renowned for missing notes and partials. This is because of all the notes that can be played with one fingering. While many of these notes will be out of tune, they can all be played. Another useful thing while playing the horn is bending the pitch. This is either making the notes a few percent sharper or flatter and is done with the mouth or embouchure. If done rapidly, it is called vibrato and adds a nice effect to a song. How do the valves and slides work?
Most horns use rotary valves which simply rotate when the key is pushed to lead to a different, extra length of tubing. The valves, when they are rotated, have holes in them that change the direction of the air stream to a longer piece of tubing. The difference between each length of tubing changes the pitch. This difference between the tubing is a certain percentage of the total length in order to lower the pitch by a whole tone. To lower the pitch by a step, the second valve must add a length of tubing 5.9% of the total length. By pressing both valves together, the length increases by 18.1%. However, to lower the pitch by three semitones, an increase of 18.9% is required. In this case, we need 0.8% more tubing for the pitch to sound in tune. For a horn player, it is necessary to move the hand to compensate for this difference in pitch.
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There is also friction associated with the valves. For this reason it is necessary to use oil on the valves. This will keep them from scraping the casing and ruining the horn. Slide grease is also necessary to put on the slides so they will move in and out freely. This also reduces the friction and scraping that can occur if the slides are not greased sufficiently. There is also compression with the slides. If the instrument is not air tight, the slides can fall out and get dented. Both the slides and the valves themselves should be air tight. The air inside the horn will keep the slides from falling out. Also, if the instrument has a leak, some of the air that the player is putting into the instrument will leak out and the instrument will not be at its maximum efficiency. Slides are also used to tune the instrument. There are so many other ways to tune the instrument that it depends on the player as to which method they like best. An instrument can be tuned by changing the pitch with the mouth or embouchure, by changing the hand position, or by using the tuning slides. Personally, I use the main tuning slide to tune one note and use my lips to bend the note one way or the other. Even if the horn player does not use the tuning slides to tune, all of them should be pulled out at least a half of an inch. How does the bell affect the sound?
The French horn is designed to keep as much of the sound that is created inside the tube as is possible. They were not designed for the radiation of sound. This is the job of the bell of the horn. The bell works on both long sound waves as well as shorter sound waves to make them sound better. A wave that is longer than the diameter of the tube is stuck in side and no sound comes out. If you add a bell to the end of the tube, then it adds a gradual increase of diameter to make a sound. The bell has to increase in equal amounts so the sound will come out. If the bell is too abrupt, the sound will stay stuck inside and will not come out. The bell also solves the problem that the notes are too far apart to be musical and the instrument is not very loud without it. The gradual increase of diameter is almost conical. Conical pipes resonate at frequencies that are higher and more closely spaced than a closed cylindrical pipe, such as the normal tubing used for the instrument. For low pitches, which resonate with long waves, the waves are longer and act differently than short waves through the bell.
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For short waves, it is easier to travel out into the open air and escape the wide bell. Faster and higher sound waves travel faster. Thus, you can easily hear a piccolo over a tuba. This is also why a trumpet plays higher than a tuba. The size of the bell makes different frequencies easier to produce. These pitches are in the range where our ears are most sensitive making brass instruments louder than woodwind instruments. However, along with a high transmission of sound comes low reflection. With low reflection, we get weak standing waves, weak resonances, and flexible notes. When any brass player tries to play higher notes, the sound gets weak and is often extremely out of tune. The bell also means that the instrument is directional. So, whichever direction the bell is pointing is the direction the sound will go. This can be used to make different sound effects. What does the hand do?
The hand in the bell is also important for the sound that comes out of the instrument. To get the clearest tone from the instrument, the hand should be cupped and placed on the outside curve of the bell. Otherwise, the tone will be altered. Without the hand in the bell, the horn will tend to be sharp. If the hand is placed too far in the horn, the pitch will be flat and the sound will be muffled. There are also different hand placements that are called for in certain songs to obtain different sounds. Stopped horn is played by putting the hand further into the bell and stopping the sound. This requires much more air to get the sizzling sound to come out. This also changes the pitch, so the player must finger the note one half step higher than the note that is written. This is written in music with a + over the note. Mutes are also placed in the bell to get this same effect. However, mutes do the transposing part for the player so it can be played as it normally would. How does the mouthpiece, tongue, and lips effect the horn?
The mouthpiece of the horn is an important part of the instrument. It includes an enclosed volume, constriction, and taper. The mouthpiece should fit comfortable on this lips of the player. Each mouthpiece has certain pitch or pop it makes when hit on the palm of you hand. Different mouthpieces have different sounds that are produced with it. The purpose of the mouthpiece is to have a large enough section to put your lips on to play the instrument. It also has acoustic effects on pitches that are higher than the pop pitch the mouthpiece makes. The enclosed volume and constriction are the two main parts
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that affect this. It strengthens some of the higher resonances as well as lowers the frequency of the extremely high resonances. Lips are springy, as they go back to their original position after you move them. The story that your mother gives you about your face sticking is fortunately untrue. Springiness and mass put together can create oscillations which is what the lips do to produce sound. The air pressure in the mouth forces the lips open and lets the air rush out into the mouthpiece. This then lowers the pressure in the mouth and also lowers the pressure in the stream of air going out of the lips. The lips then close again due to their elasticity and the pressure in the mouth builds up once again. The cycles then repeats.
The tension used on the mouthpiece is also important for the sound that is produced. The more tension you apply to your lips, the more quickly they spring back into position. If the whole cycle takes a time T (called the period), then there are (one second)/T cycles per second. So the frequency f, in cycles per second, is just f = 1/T. High lip tension gives high frequency and thus creates a high pitch. This however, is the incorrect way to play higher notes. If you tighten the lips, this creates a pinched sound. The correct way is to use more air and not as much pressure. A mouthpiece makes relatively minor changes as it can reduce the amount of the lips that move, and it allows the pressure outside the lips to be a little different from atmospheric. The best way to position the mouthpiece is asymmetrically, so that it covers more of the upper lip than the lower lip. The tongue is also important in playing the French horn. There are two ways to “tongue”. The purpose of tonguing is to stop the sound. This can be accomplished by either stopping the air flow, using the throat to stop the air flow or using the tongue to st op the air flow. The most convenient and useful way of tonguing is by using the tongue to stop the air. This is much better for fast music. There are also methods such as double and triple tonguing. This is when a combination of throat and tongue is used to produce a very rapid succession of notes. How do different metals affect the sound?
Some players prefer a brass horn while others prefer a silver horn and still others a lacquered horn. Each metal affects the sound in a different way because of the different vibrating qualities of the
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metals. There are lacquered horns, horns plated in gold or silver, and horns that are bare metal. Each player has his or her preferences as to which horn they like better. An experiment was done where three identical instruments were put in the three different coatings. It was found that plain brass and silver or gold plated instruments played exactly the same. However, a lacquered instrument changed the tone a bit. The tone was impaired and the over all pitch was changed. This is because the lacquer is very thick on an instrument. It changes the quality and resonance of the bell. It is unlike the original brass to begin with so the amount of lacquer that goes on the instrument changes it to a new instrument with a non brass bell. How is the loudness measured?
In written music, musicians are given certain loudness markings or dynamics to follow. A forte (f ) means loud, piano ( p) means soft. Mezzo ( m ) is added to these to mean moderately, for example, Mezzo forte (mf ) means to play moderately loud. During these changes, the pitch does not change, just the loudness that the note is being played. The change from loud to soft is called a decrescendo and a change from soft to loud is called a crescendo. The scientific way to measure the level of sound it with decibels (dB). dB is a logarithmic unit used to describe a ratio of two measures of the sound. The ratio may be power, sound pressure, voltage or intensity or several other things. In this case, we are measuring the amount of sound pressure. The difference of one decibel is quite hard to distinguish, thus decibels are rarely measured in increments smaller than 1 dB. This can also be measured as the intensity of sound. 10 decibels is equal to 1 bel, named after Alexander Graham Bell. This can also be written in the units, Watts per meter squared. To make a crescendo noticeable during a piece of music, the musician must increase the sound by at least 8 decibels. However, in the higher range of notes, the difference is even harder to tell so the musician may have to increase the sound by as much as 45 decibels. Decibels are also directly related to the atmosphere and atmospheric pressure. While 120 dB can be a painfully loud level of sound, it may not be a problem when the atmospheric pressure is different. To determine the loudness of a sound, one needs to consult the curves representing the frequency response of the human ear. Loudness is measure by the amplitude or height of the sine curve. Loudness and intensity are different however. Sound intensity is objective, while loudness is a physiological sensation. What is timbre and the quality of sound?
It is not difficult for people to tell the difference between a tuba and a piano. This is because each instrument has its own quality or timbre. Each instrument, when it sounds one note, has a variety of other 9
notes that can be. A middle C on a piano is about 262 Hz. It also has a blend of other partial tones that also ring at the same time. A pure tone with only one frequency can only be produced electronically. This is how we can tell different instruments apart. If both a piano and a horn play a C, the horn will have different frequencies ringing than the piano and will creating a different sound. In order to get the best quality of sound on a horn, the lips need to be placed correctly with the right amount of tension and the amount of air blown should be enough to produce a good sound. For the lips and the mouthpiece, first you need to say the letter “m” This puts the lips in the best formation for sound. Place the mouthpiece on the lips and blow air. There must be a vibration for the sound to come out. A poor quality sound can be made by not enough air, too much tension in the lips, a restricted throat, and very rarely, too much air. These problems can usually be solved by taking a bigger breath and blowing more air through the instrument. This, as well as relaxing the throat and lip tension, will solve most problems associated with tone. What do I change when playing with an ensemble?
When an individual plays with other people, he or she has to listen to play in tune with the other players. While a horn player may be in tune exactly, according to a tuner, he will probably be out of tune with the other players in the ensemble. The pitches of each interval must a certain length apart in order to sound good to our ears. For example, some chords are structured so that the third of the chord needs to be played lower than usual for it to sound good to our ears. Also, when playing with other players, the sound levels are relevant to the rest of the band. A forte in a solo piece will be much louder than a forte in a group of players. The dynamics are not a certain decibel level, but a relative measurement. Playing with a piano accompanist is very different from playing with a 40 instrument band. With a band there are certain balances that sound best with each song. A pyramid of sound is used in most tunes. This is where the low instruments like trombones and tuba are the loudest, and the higher instruments, such as trumpets and flutes play softer. There are many different sound “shapes” that can be made.
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French horns are usually considered to be a part of the middle section although, because of the large range of a horn, they can be included in the high and low ranges as well. When two or more instruments are played together, the two different frequencies combine. While on a picture of the frequencies, it is hard to tell them apart, our ears can distinguish the different sound that each unique instrument makes. The French horn is a unique instrument as most of the sound is directed to one side. For this reason, it is important to put the bell closest to the audience for the best sound. Also, a horn player hears a different balance than the director hears at the front of the ensemble. It is important for the player to listen carefully to the balance of the rest of the band. However, horn players rarely are told that they are playing too loud. Because of all of the tubing that horns have, it is more difficult to play loudly. Also, horns have a more mellow sound than all of the other instruments making it more difficult to hear. It is often used as an instrument to fill out the sound of the chord. It is f elt in the music more than it is actually heard.
In conclusion, it is fascinating how everything we do has some sort of physics involved in it. We rarely think about why and how things work the way they do. We always just take it for granted. This paper has been very informational for me and has helped me understand my favorite instrument a little better than before.
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BIBLIOGRAPHY
Author: Joe Wolfe Title: Brass instrument (lip reed) acoustics: an introduction Date of publication: Oct-Mar 2005 Place of publication: The University of New South Wales. Website URL:
Author: Matthew Panayiotou Title: Articles - The French Horn Date of publication: 2005 Place of publication: London Website URL:
Author: Leah Norwood Title: Horn Harmonics Place of Publication: California Website URL:
Author: Paul G. Hewitt Title: Conceptual Physics, 10th edition Publisher, place of publication, date of publications or copyright date: Published by Pearson Education Inc. in United States of America, copyright 2006. 12
