What is a beat frequency?

Beat frequency is the rate at which the amplitude of a combined wave rises and falls due to interference between two waves at slightly different frequencies. It equals the absolute difference: f_beat = |f1 - f2|.

What is the beat period?

The beat period (T_beat) is the time between successive amplitude peaks of the beat envelope. It is the reciprocal of beat frequency: T_beat = 1 / f_beat. For example, a 2 Hz beat has a period of 0.5 seconds.

What happens when f1 equals f2?

When both frequencies are identical, the beat frequency is 0 Hz — no beats occur and the waves reinforce each other continuously (constructive interference). The beat period is undefined (infinite).

What is the practical limit for audible beats?

Humans typically perceive beats clearly when f_beat is below about 15–20 Hz. Above that, the ear starts to perceive the two frequencies as distinct pitches rather than a single pulsing tone.

Can I use this for non-sound waves?

Yes. The beat-frequency formula applies to any two sinusoidal waves of similar frequency — radio signals, light waves, or electrical oscillations — whenever they are superimposed.

Beat Frequency Calculator

Calculate the beat frequency and beat period when two sound waves of slightly different frequencies interfere.

Frequencies

First frequency f₁ (Hz)

Second frequency f₂ (Hz)

Examples

Results

Enter two frequencies and press Calculate.

Summary

Calculate the beat frequency and beat period when two sound waves of slightly different frequencies interfere.

How it works

Enter the first frequency (f1) in Hz.
Enter the second frequency (f2) in Hz.
The calculator computes f_beat = |f1 - f2|.
The beat period is shown as T_beat = 1 / f_beat.
Click Calculate or press Enter to update the results.

Use cases

Tune musical instruments by listening for and eliminating beats.
Analyze acoustic interference in architectural acoustics.
Study wave superposition in physics coursework.
Verify frequency differences between two oscillators or signal generators.
Determine the beat period for timing experiments.
Understand why two slightly detuned guitar strings sound "wobbly."

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu