Disturbance of the particles of any elastic body may result in the production of sound waves. The pitch of the sound will depend chiefly on the elasticity of the body and on its mass. When the body consists of a volume of air confined within elastic walls and under the pressure of the atmosphere, its elasticity may be considered to be constant. In this case the pitch of its proper, or fundamental tone is determined by the volume of the contained air if one of the dimensions of the cavity does not greatly exceed the others. In tubes, the diameter remaining unchanged, the pitch of the fundamental tone is determined chiefly by the length of the tube, the longer the tube, the lower the pitch.
The resonator of the physicist is an apparatus used for the analysis of sounds into their component tones. The ideally perfect resonator answers only when