The Physics of Playing French Horn

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Transcript of The Physics of Playing French Horn

The Physics of Playing French Horn

Title: The Physics of Playing French Horn

Name: Bethany DeiblerDate: May 30, 2008Spring quarterClass:Physics 100Sidibe, 9:10WORKING TOWARD: A

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 17th 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 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 pianos 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 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 dont 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 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 horns 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