Acoustic Beat Period Calculator

About this calculator

When two tones of slightly different frequencies (f₁ and f₂) sound together, their amplitudes periodically reinforce and cancel, producing an audible pulsing called a beat. The beat frequency equals the absolute difference between the two tones, |f₁ − f₂|, the beat period is its reciprocal (1 ÷ beat frequency), and beats per minute is simply the beat frequency multiplied by 60.

Piano and instrument tuners use audible beats as their primary tuning reference: when tuning a unison or octave, they adjust a string or pipe until the beat frequency slows to zero (or to a specific target rate for tempered intervals), since a trained ear can judge beat rate far more precisely than pitch alone. The same phenomenon explains the throbbing “wah-wah” sound of two closely tuned musical instruments playing together, and physicists use it to demonstrate wave interference.