Formation of Beats

Beats (periodic rise and fall in intensity) are produced when two waves of nearly equal frequency are added. The beat frequency is the difference of the two frequencies, while the resultant waveform itself varies at the average of the two frequencies.

In this applet, the two waves are emitted from two near point sources.

The two sinusoial waveforms before addition and/or the resultant waveform will be displayed in turn by clicking anywhere on the pattern .

The reciprocal of the number "difference in freq / mean frequency" is the number of cycles between two consecutive points of zero intensity.

Do you "see" the beat?