By Zencalcy Editorial TeamLast reviewed About us
Two steady tones close in frequency interfere to produce a slow amplitude pulse called a beat. The loudness rises and falls at the difference frequency, which musicians use to tune strings and which technicians use to align oscillators. Wide separations stop sounding like a beat and become two distinct pitches.
Difference frequency heard when two tones nearly match.
f_beat = |f₁ − f₂|
The beat rate is the absolute difference. The perceived pitch sits near the average of the two tones, and the amplitude envelope completes one cycle per beat.
| Symbol | Meaning |
|---|---|
| f_beat | Beat or difference frequency. |
| f₁ | First tone frequency. |
| f₂ | Second tone frequency. |
The beat rate is 4 Hz, so the loudness peaks four times per second. Tuning one string until the beats slow and vanish brings it to the other pitch.
Continue with the Decibel Addition Calculator, Doppler Effect Calculator, or the Sound Distance Attenuation Calculator — or browse more acoustics and sound tools and all physics calculators.
The ear's frequency resolution is finite. When two components fall within a critical band, they are not separated into distinct pitches; instead their sum rises and falls at the difference frequency.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Free calculator · No signup
Content updated: September 2026