Beating
Slow pulsations in loudness heard when two close frequencies interfere, at a rate equal to their difference in hertz.
Also called: beat frequency, acoustic beats, interference beats
Beating is the slow pulse in loudness heard when two tones of nearly equal frequency sound together. The waves reinforce and cancel in turn, so the combined sound swells and fades. The number of beats per second equals the difference between the two frequencies. Tones at 440 Hz and 443 Hz produce three beats per second, and tones at 440 Hz and 441 Hz produce one. Tuners use this to match strings. They adjust one string until the beats slow and disappear, which means the two frequencies agree. Beating is not the same as the beat of a meter. Here the word refers only to the interference pulse, which is too slow to be heard as a rhythm once the frequencies are far apart.
Related terms
- FrequencyThe number of complete vibration cycles per second, measured in hertz (Hz), which sets a sound's pitch.
- ResonanceA body or air column vibrating strongly when driven near its natural frequency, which boosts that frequency.
- Equal temperamentA tuning that divides the octave into twelve equal semitones of 100 cents, so every key sounds alike and no interval is pure.