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How does it all work together? This is a brief introduction to the unique factors in creating the clarinets’ signature sound—decoding the art of the musician and the scientific physics of sound, vibration and pitch.
How do clarinets make sound?
The clarinetist places their lips around the mouthpiece and reed creating an airtight seal. Air is pushed past the mouthpiece and reed through the instrument. This rush of air forced past the reed of the clarinet will vibrate rapidly, like a flag flapping in the wind, creating sound. The column of air inside the clarinet mimics the vibration of the reed, and we hear musical notes float out of the bell.
Sound can be thought of as the brain’s understanding of vibrations in the air. Imagine a piece of string. If you run a bow across it or pluck it, it vibrates. Similarly, if you blow down a hollow tube or cause air to move through it, it also vibrates.
If you try this yourself with some string or a kitchen roll tube you will be able to hear a faint sound while the object is vibrating. When you ring a bell or tap on glass, you hear this sound because the air next to your ear is vibrating.
All sound depends on the presence of air. The vibrating object causes the air next to it to vibrate at the same speed. That air causes the next bit of air to vibrate, and so on, until the air next to your ear is vibrating. Astronauts can only play instruments, or I should say, hear instruments, if air is present. So even if you carried a piano up to the space station, it would only produce sound in an “air-having” environment.
Plucking a single string produces only a very small sound. This is because the string does not move much air. To create a louder sound the string needs to pass its vibrations to something bigger that will also vibrate. For example, with a violin the strings are attached to a hollow wooden box. When plucking a violin string, the sound is much louder than with our one piece of string. This is because the violin string’s vibration is passed not only directly to the air next to it, but also down into the hollow box. The vibrations of the hollow box make a lot more air vibrate than the string alone, so when the vibration reaches your ear it seems much louder.
A clarinetist when creating a sound, in general, wants to make the reed vibrate as much as possible, creating a warmer, fuller, and probably louder resonance.
How does pitch affect sound?
The measurement of how often a sound wave passes by per second (cycles per second (cps)) is called the frequency (frequency is measured in a unit called hertz (Hz)). Pitch is created by the speed and size of vibrations. Pitch is how low or high we perceive a sound to be. If the pitch is higher, that is because the frequency is faster.
Sound travels slower than light. Though sound waves do all travel at the same speed, they vibrate in different ways. Plucking a short piece of string will produce a higher sound than a long piece of string, because the vibrations from the shorter piece are smaller and faster. The same is true for blowing into a shorter tube. With a longer piece of string or tube the vibrations are bigger and move more slowly and the sound will be lower. Different pitches are the result of using different lengths of string and tube. This forms the basis of pitch production for stringed instruments such as the violin and cello and event the piano, and for brass instruments such as the trumpet and trombone.
Violinists use their fingers to change the length of the string. Trumpeters use valves to change the length of a tube, allowing air to travel down shorter or longer tubes. The most obvious example of this is the trombone. You can literally see the trombonist extending the length of the instrument in order to change the pitch. Brass players can also vary the speed of the air that they blow into the tube to yield different pitches.
How is pitch adjusted in wind instruments?
Wind instruments, such as the flute and clarinet, are slightly different and more complex. Sound is still made by vibrations, but the length of tube for these instruments is fixed. Clarinets have reeds in their mouthpieces. When the clarinetist pushes air over the reed, it begins vibrating. This vibrating reed forces all the air in the clarinet to vibrate. The speed and size of vibrations produced is controlled by covering and uncovering holes in the tube. It is the combination of holes covered that generates different types of vibrations and thus different pitches. Like brass players, wind players also control the pitch by varying the speed of the air that they blow into the tube.
Does the shape of the clarinet affect the sound?
Your clarinet is a fascinating and beautiful instrument. The unique clarinet shape totally effects the sound that is produced. If you have ever talked into a cardboard tube or into a soda bottle you know that sound is changed by the shape.
The smaller the instruments the higher the sound in general. A larger instrument will produce a deeper sound. This is not confined to just clarinets but is true for any instrument.
Clarinets have a conical bore. What this means is as you move lower down the clarinet ,the internal hole (bore) radius becomes larger. Your clarinet is basically a hollow tube. It has roughly the same width all the way down, except the space (aperture) between the reed and the mouthpiece is much narrower, and then the larger bell at the base. The conical bore in a clarinet makes some harmonic frequencies loud and some not.
The clarinet tone holes that are all down your instrument also affect the pitch of the sound. The wavelength of your sound waves are increased and the pitch is lowered as more of your tone holes are covered.
For more insight
If you are enjoying learning about sound waves from your clarinet and want to know more about the physics, visit this link.