Tuning Forks

Tuning forks are acoustic amplifiers with many uses usually in the shape of a U form. Made of Elastic metal Usually steel, When they are struck against an object they begin vibrating at a specific constant rate. the pitch depends on the length and mass of the prongs, they are used to tune instruments. They were invented in 1711 by a british musician , John Shore. 

They also have many other uses along with being used in watches, alternative medicine like sonopuncture and polarity therapy, along with the use of calibrating radar guns. 

They have been put to the side now that the electronic tuners have come into play, although there is a way to make tuning forks electronic. Can take electromagnets and place them close to the prongs that are attached to an electric oscillator circuit, so the sound does not die out