Vibration is rapid to and fro movement of an object. This helps in the transmission of sound waves, which travel to our ears. Sound is a form of energy that is produced when an object vibrates. For example, vibration of guitar strings produces pleasant sounds.

Amplitude is the maximum displacement moved by a vibrating body from the mean position. The energy of a wave is proportional to the square of the amplitude. Loudness of a sound wave directly proportional to the square of the amplitude of the sound wave.

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.