Many musical instruments have pipes. When air inside a pipe is vibrated, it produces a sound. The traditional organ is probably the best-known instrument that consists of columns of air, but other examples are found throughout the orchestra. They include wind instruments, such as recorders, oboes, and clarinets, and brass instruments, such as trumpets and trombones. In an organ, there are a number of hollow pipes; each one has a different length. When air is blown across the bottom end of a pipe, the air inside the pipe vibrates. The length of the pipe determines the note produced by the vibrating column of air. The shorter the pipe, the less air there is to vibrate and the higher the note. A long pipe contains a greater volume of air and vibrates more slowly, producing a lower note.
Very rapid vibrations produce high pitch sounds and lower pitch sounds are the products of slower vibrations. When a number of vibrations are initiated with approximately the same force the speed of the vibrations depends upon the amount of matter being vibrated. A greater amount of matter will vibrate more slowly than a lesser amount of matter when vibrated by the same amount of force. In the case of the panpipes it is the air inside the pipes that vibrates. The longer pipes have more air inside them, so when they are blown into the air vibrates slowly and produces a low note, compared to the shorter pipes. Test this by blowing equally hard into each of the pipes and listening to the difference in the sounds. Then, increase the rate of vibration by blowing twice as hard into each pipe. For each pipe a higher sound will be heard than when blowing without so much force.
"SOUND: Science Projects." Simon de Pinna, Raintree Steck-Vaughn Publishers: Austin, 1998, p. 32.
© S. Olesik, WOW Project, Ohio State University, 2000.
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