CBSE Class 11-science Answered

When two waves of nearly equal frequencies, travelling in same direction superimpose, the intensity of sound at a point change with time periodically.  The periodic variation in intensity of sound is called beats.

One loud sound followed by one faint sound or one faint sound followed by one loud sound constitutes a beat.

Time lapsed between two successive loud sounds or two faint sounds are called beat-period and reciprocal of beat sound is called beat frequency.

Analytical treatment of beats :

Let two waves be represented by