The pitch of a tuning fork can vary slightly with weathering and temperature. Well-known manufacturers of tuning forks include Ragg and John Walker, both of Sheffield, England. Standard tuning forks are available that vibrate at all the musical pitches within the central octave of the piano, and other pitches. Tuning forks used by orchestras between 17 mostly had a frequency of A = 423.5 Hz, although there were many forks and many slightly different pitches. Filing the ends of the prongs raises the pitch, while filing the inside of the base of the prongs lowers it.Ĭurrently, the most common tuning fork sounds the note of A = 440 Hz, because this is the standard concert pitch, which is used as tuning note by some orchestras, it being the pitch of the violin's second string, the first string of the viola, and an octave above the first string of the cello, all played open. If a sound absorbing sheet is slid in between the prongs of a vibrating fork, reducing the waves reaching the ear from one prong, the volume heard will actually increase, due to a reduction of this cancellation.Īlthough commercial tuning forks are normally tuned to the correct pitch at the factory, they can be retuned by filing material off the prongs. The reason for this is that the sound waves produced by each fork prong are 180° out of phase with the other, so at a distance from the fork they interfere and largely cancel each other out. Without the resonator the sound is very faint. The fork is usually struck, and then the handle is pressed against a wooden box resonator, or a table top. The handle motion is small, allowing the fork to be held by the handle without damping the vibration, but it allows the handle to transmit the vibration to a resonator, which amplifies the sound of the fork. There is a node (point of no vibration) at the base of each prong. It is easier to tune other instruments with this pure tone.Īnother reason for using the fork shape is that, when it vibrates in its principal mode, the handle vibrates up and down as the prongs move apart and together. So when the fork is struck, little of the energy goes into the overtone modes they also die out correspondingly faster, leaving the fundamental. By comparison, the first overtone of a vibrating string or metal bar is only one octave above the fundamental. The reason for this is that the frequency of the first overtone is about 5 2/2 2 = 25/4 = 6¼ times the fundamental (about 2½ octaves above it). The main reason for using the fork shape is that, unlike many other types of resonators, it produces a very pure tone, with most of the vibrational energy at the fundamental frequency, and little at the overtones ( harmonics). A needle on a tuning fork carves figures on carbon black.

Tuning fork c512