A variety of tuning fork sets and tuning fork pair with resonance box for the study and demonstration of sound and frequency.
(Wiki excerpt….”..A tuning fork (TF) 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 once the high overtones fade out. A (TF) pitch depends on the length and mass of the two prongs. They are traditional sources of standard pitch for tuning musical instruments….The (TF) was invented in 1711 by British musician John Shore, Sergeant trumpeter and lutenist to the court….
Currently, the most common (TF) sounds the note of A = 440 Hz, the standard concert pitch that many orchestras use. That A is the pitch of the violin’s second string, the first string of the viola, and an octave above the first string of the cello. Orchestras between 1750 and 1820 mostly used A = 423.5 Hz, though there were many (TF) and many slightly different pitches… Standard (TF) are available that vibrate at all the pitches within the central octave of the piano, and also other pitches….(TF) pitch varies slightly with temperature, due mainly to a slight decrease in the modulus of elasticity of steel with increasing temperature….”)