HesapHanem

Beat Frequency Calculator

Find the beat frequency of two tones.

How it is calculated

When two tones of close pitch sound together, the loudness swells and fades at the beat frequency: fbeat = |f1 − f2|. Both f1 and f2 are frequencies in hertz (cycles per second), and the answer is also in Hz, meaning pulses per second. The tool takes the absolute difference, so the order of the two inputs does not matter; neither frequency may be negative. The result is shown with two decimals. The effect is easy to hear only when the difference is small, roughly a few hertz; for large gaps you hear two separate pitches instead.

Worked example

A guitarist tunes a string against a 440 Hz reference, and the string is slightly sharp at 442 Hz. The difference is 442 − 440 = 2. The tool shows 2.00 Hz: you hear two slow swells in loudness every second. As the string is tuned closer to 440 Hz, the beats get slower and disappear when both frequencies match.

Try this example →

Common mistakes

  • Subtracting the wrong way and getting a negative beat rate. The beat frequency is always the absolute difference, never negative.
  • Entering note names or periods instead of frequencies. Both fields need hertz, not seconds or milliseconds.
  • Using the sum or average of the frequencies. Beats follow the difference; the average only describes the perceived pitch.
  • Expecting audible beats for tones far apart. If the gap is large, you hear two distinct notes rather than a pulse.
  • Mixing units, such as kHz for one tone and Hz for the other. Convert both to Hz first.

About this calculator

When two sound waves of slightly different frequencies overlap, they periodically reinforce and cancel each other, producing a rhythmic pulsing in loudness called a beat. The beat frequency is simply the absolute difference between the two frequencies, |f₁ − f₂|, in hertz — two tones at 440 Hz and 444 Hz produce 4 beats per second. This happens because of wave interference: the combined waveform can be written as a product of a fast average-frequency oscillation and a slow envelope oscillating at the beat frequency.

Musicians and piano tuners use beats constantly: when tuning a string or instrument to a reference pitch, they listen for the beating to slow down and disappear as the frequencies converge — a technique far more precise than reading a tuner's needle. Physics students and acoustic engineers also use beat frequency to analyze interference, measure small frequency differences between oscillators, and explain phenomena like the wavering sound of two slightly detuned guitar strings.

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Comments (1)

  • Editorial team

    The result is an absolute difference, so it tells you how fast the beats are but not which note is sharp. When tuning by ear, nudge one string slightly and listen: if the throbbing slows down, you moved the right way. Beats are easiest to hear when the two pitches are a few hertz apart, and they blur into a rough tone as the gap widens. Are you tuning an instrument or checking two oscillators?

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