Beats

Theory

Constructive and destructive interference can be measured as a function of time not just space

A beat is the change in amplitude caused by two or more waves with different frequencies

The amount the amplitude changes is relative to the difference in the frequencies of the individual sound waves.

Theory

As shown in the figure, theBlue and red waves are creatingconstructive and destructiveinterference resulting in thegreen wave, which is the amplitudewe hear.