The maximum displacement of a vibrating object from its mean position is called the amplitude of vibrations. In other words amplitude actually tells us how far the vibrating object is displaced from its equilibrium position. Amplitude is measured in metres. The loudness of sound has a direct dependance with the amplitude of vibrations.

The time period is defined as the time taken by a vibrating object to complete one vibration. One complete to-and-fro movement of the pendulum bob is called one vibration. It is denoted by T . The time period is the reciprocal of frequency and it is measured in seconds.

The number of vibrations produced by a source of sound in one second is called the frequency. It depends on the time period of vibrations but does not depend on the amplitude of the wave. Frequency is denoted by f or n . The SI unit of frequency is hertz.