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tuning fork,steel instrument in the shape of a U with a short handle. When struck it produces an almost pure tone, retaining its pitch over a long period of time; thus it is a valuable aid in tuning musical instruments. It was invented in 1711 by John Shore, who jokingly called it a pitchfork.
A steel instrument consisting of two prongs and a handle which, when struck, emits a tone of fixed pitch. Because of their simple mechanical structure, purity of tone, and constant frequency, tuning forks are widely used as standards of frequency in musical acoustics. In its electrically driven form, a tuning fork serves to control electric circuits by producing frequency standards of high accuracy and stability. A tuning fork is essentially a transverse vibrator (see illustration). See Vibration
a source of sound, consisting of a metal rod that is bent and fixed in the center. The ends of the rod can vibrate freely. During the tuning of musical instruments, the tuning fork serves as the standard pitch of a tone; it is also used to give the pitch in singing. Forks that produce the tone A’ (A of the first octave) are usually used. Singers and choral conductors also use forks producing the tone C”. There are chromatic tuning forks, with prongs that have movable little weights. Depending on the position of these weights, the prongs vibrate at different frequencies.
The tuning fork was invented by the English musician J. Shore in 1711. At that time the standard frequency of vibrations for the tone A’ was 419.9 hertz (Hz). In the late 18th century the composer and conductor G. Sarti, who was working in St. Petersburg, introduced the “St. Petersburg tuning fork,” with an A’ = 436 Hz. In 1858 the Paris Academy of Sciences proposed a standard pitch tuning fork with A’ = 435 Hz. In 1885 at an international conference in Vienna this frequency was adopted as the international standard pitch for the tone A’; the frequency was called the standard musical pitch. Since Jan. 1, 1936, an all-Union standard pitch of A’ = 440 Hz has been in effect in the USSR.