Sonometer consists of a hollow rectangular wooden box of more than one-meter length, with a hook at one end and a pulley at the other end. One end of a string is fixed at the hook and the other end passes over the pulley. A weight hanger is attached to the free end of the string. Two adjustable wooden bridges are put over the board so that the length of string can be adjusted.

Production of transverse waves in stretched strings:

If a string of length l having mass per unit length m is stretched with a tension T, the fundamental frequency of vibration f is given by

Laws of transverse vibrations on a stretched string:

Law of Length:
The frequency of vibration of a stretched string varies inversely to its resonating length (provided its mass per unit length and tension remain constant.)

Law of Tension: The frequency of vibration of a stretched string varies directly as the square root of its tension, (provided its resonating length and mass per unit length of the wire remains constant).