Beat



When two sound waves of same amplitude and nearly equal frequency move in the same direction then these two waves superimpose to each other giving rise to alternating hearing of the sound. This phenomenon is called Beat.

The no of hearing produce in one second is beat frequency.

beat

beat

Consider two waves having frequency f1 and f2 then the displacement equation of these two waves are given by.

beat

If the two waves are sounded together, they will interfere and the resulting displacement y according to the principle of super position is given by,

beat

Since, intensity of sound is related to the amplitude of sound.

 Condition of maximum intensity:

The intensity will be maximum.

beat

beat

i.e. the intensity of sound will be minimum in the time

beat

 

The consecutive time internal between the hearing two minimum intensity of sound

beat

 

Since the consecutive time internal between maximum or minimum intensity of sound is called beat period.

beat