The Savart wheel is an acoustical device that was created by French physicist Félix Savart (1791-1841), which he used for research on lower frequency limits of hearing.
The device consists of a mounted metal disk having a large number of teeth with uniform spacings on its circumference. When the toothed disk is spun in rapid revolution, and an edge of a playing card is held against the teeth, it produces a shrill tone. When the speed of the wheel slows down, the shrill tone correspondingly diminishes in pitch. Thus, the frequency in tone is directly proportional to the rotation rate of the disk.
A variation of the Savart wheel has a series of toothed wheels which can be used to produce the sound of a major chord.
* Source: Elroy M. Avery, School Physics (New York: Sheldon and Co., 1895)
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