Beat

Beat, in Music. (A) The name given to a peculiar turn employed in old music. (B) An acoustical phenomenon due to the interference of sound waves. If two notes of very nearly the same pitch be sounded together, the effect produced will be that of a single throbbing note with rapid periodic variation in intensity. It may often be observed in the clang of bells. The number of throbs, or beats, is equal to the difference in the frequencies of the two notes. Thus if one note is produced by 256 vibrations per second and another by 258, when the two are sounded together two beats per second will be heard. A similar effect is produced when the frequencies, instead of being nearly equal, are very nearly in some simple ratio to each other. This effect supplies a method for the estimation of the frequency of a note. (C) The movement of the hand or baton in counting time, (D) Also the several divisions of the notes in a bar of music, according to the time-sign indicated.