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"The Physics of Music"	Page 1	copyright: David F. Bills 1997

Vibration is the source of all sound. The source of sound in the violin, oboe, and timpani drum is an audible, periodic vibration in each case. When vibrations are generally periodic, meaning that they are moving with a recurring pattern, the human ear perceives sound. (Plomp, 1964)

In class laboratory, we looked at the constant motion of a pendulum. This is one of the simplest examples of vibration and related properties. When the pendulum was raised and then set in motion, it began swinging back and forth. Observation revealed a regularly occurring cycle. This was the journey of one period. The number of cycles in an amount of time was the frequency and the vertical distance from the original height of the pendulum to the furthest displacement is the amplitude.

The same phenomena occur musical instruments, but at a much higher rate where the individual cycles are not visible. The sounds of music are complex combinations of these cycles in periodic events called notes. The vibrational waves that make up an individual note are transmitted longitudinally through the air from the sound source to the listener. The overall propagation of the wave travels in the same direction as the air particles. This series of air disturbances is referred to as a sound wave.

The human ear can "hear" sounds in the frequency range of about 20 to 20,000 hertz. Using the equation: , it can be determined that the lowest audible note, at 20 hertz, would arise from a 17 meter wavelength. The highest note, at 20,000 hertz, would come from a wavelength of 0.017 m. An organ producing these tones would use pipes that are approximately one-half of the desired wavelengths, 8.5 meters and 0.0085 meters. Most full-sized organs have pipes ranging from about 8 meters to 0.05 meters in length. (Trefel & Hazen, 1995) Due to the extremely high frequencies produced by the smaller pipes, they are sometimes removed because of the interference they produce in hearing aids.

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"The Physics of Music"	Page 1	copyright: David F. Bills 1997