A
tuning fork is an
acoustic resonator in the form of a two-pronged
fork with the prongs (
tines) formed from a U-shaped bar of
elastic metal (usually
steel). It
resonates at a specific constant
pitch when set vibrating by striking it against a surface or with an object, and emits a pure musical tone after waiting a moment to allow some high
overtones to die out. The pitch that a particular tuning fork generates depends on the length and mass of the two prongs. It is frequently used as a standard of pitch to tune musical instruments.