What causes beats?
Two tones of nearly equal frequency add to a sound that pulses in loudness. The pulse rate is the beat frequency, f_beat = |f₁ − f₂|.
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Sound Beat Frequency
Find the beat frequency of two close tones, f_beat = |f₁ − f₂|, and see how the two waves combine into a pulsing envelope.
f_beat = |f₁ − f₂|; sin(2πf₁t) + sin(2πf₂t)
Frequently asked questions
What is the trig behind it?
sin(2πf₁t) + sin(2πf₂t) factors into a fast tone at the average frequency multiplied by a slow envelope at half the difference — that envelope is the throb you hear.
Can you show a worked example?
440 Hz and 444 Hz give f_beat = |440 − 444| = 4 Hz — four loudness pulses every second.
How do musicians use beats?
When tuning, two strings near the same pitch beat slowly; as they approach unison the beats slow and vanish. No beats means the pitches match.
Why no angle toggle here?
This calculator works with frequencies and time, not an angle, so there is no degrees/radians choice to make.