The periodic signal produced by interference when two signals of slightly different frequencies are combined. The amplitude is equal to the sum of the original amplitudes; the frequency (the beat frequency) is equal to the difference between the original frequencies. The production of beats is termed beating and is achieved, for example, by using a beat-frequency oscillator. This device incorporates two radiofrequency oscillators, one producing a fixed frequency wave and the other a variable frequency; the output is produced by beating together the two frequencies.
Beating is also the basis on which a musical instrument is tuned by reducing the beats with a reference to 0 Hz by adjusting, for example, the string or pipe length.