Tuning Beat Rate Calculator

Two sustained pitches beat because one partial of the lower note and one partial of the upper note land close together: the two waves add and cancel at the difference frequency, so you hear loudness pulse at |p × f lower − q × f upper|. For a just perfect fifth that pair is the lower note's third partial against the upper note's second, which is why 3 × 220 = 660 Hz and 2 × 330.5 = 661 Hz give exactly one beat per second. The partial numbers are fixed by the interval, so the same cents error beats faster in a higher octave and faster for wider intervals: a fifth at A3/E4 gives about 0.7 beats per second when equal temperament is in tune, and roughly double that an octave up. This page assumes ideal harmonic tones with partials at exact integer multiples; real strings are slightly inharmonic, piano tuning spreads octaves to compensate, and a struck note decays, so measured beats drift and are not a substitute for a trained ear, a tuner or the instrument's own service instructions. Everything is computed in your browser: nothing is played, stored or sent anywhere.