AudioTestPro

Multiple tone generator

Play up to six tones together, each with its own frequency, level and stereo position. Hear beats between close pitches, build intervals and chords, or run a two-tone distortion test.

Volume first. Turn your device volume down before pressing play, then raise it slowly. Tones start quiet on purpose. Keep headphones off your ears until you know how loud it is.

2 tonespeak sum -24.0 dBFS · beating 4.0 /s
A4
A4

Things to try

  • Hear beats: load "Beats", then move tone 2 from 444 towards 440 Hz. The wobble slows and vanishes when the pitches match. This is how piano tuners and guitarists tune by ear.
  • Binaural vs acoustic beats: pan tone 1 fully left and tone 2 fully right and listen on headphones. The wobble changes character because it is now made by your brain, not the air. The binaural beats generator explores this.
  • Intermodulation distortion: the SMPTE RP120 style test mixes 60 Hz and 7 kHz at a 4:1 amplitude ratio (12 dB apart). A clean system reproduces only those two; a distorting one adds sidebands at 7 kHz ± 60 Hz, ± 120 Hz, visible on a second device running the spectrum analyzer.
  • Intervals: a perfect fifth is a 3:2 frequency ratio, an octave 2:1. The equal-tempered major chord in the preset is very slightly off pure ratios, which you can hear as slow beating.

Questions people ask

What is a multiple tone generator for?

Playing two or more frequencies at once lets you hear beating between close tones, build chords and intervals, test intermodulation distortion (classically 60 Hz plus 7 kHz at a 4:1 level ratio, the SMPTE IMD test), or reproduce dual-tone signals such as telephone DTMF and dial tones.

Why do two close tones make a wobble?

When two frequencies differ by a few hertz, their peaks drift in and out of step, so the combined loudness rises and falls at the difference frequency. 440 Hz and 444 Hz beat four times a second. Musicians tune by slowing the beats until they disappear.

Will the combined tones clip?

Each tone has its own level, and the levels add. Keep the total below about −6 dBFS. A limiter on the output prevents harsh digital clipping, but it will squash loud combinations.

Can I download the result?

Yes. "Download WAV" renders the current set of tones on your device as a 48 kHz, 16-bit stereo file of the length you choose.

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