DTMF Tones

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DTMF Tones generates dual-tone multi-frequency (DTMF) tones like those produced by the keypad on telephones.
Advice Note carefully that when you apply a Generator to a selected time-stretched clip the changed speed of the clip will be automatically rendered.
  • If you apply a Generator to a selection within a time-stretched clip then Audacity will split the original clip so that the selection can be rendered as part of applying the Generator
Accessed by: Generate > DTMF Tones
DTMF Tones 3-5-0.png

DTMF sequence

For each tone you wish to generate, enter numbers from 0 to 9, lower case letters from a to z, and the * and # characters. You can also enter the four "priority" tones used by the US Military (upper case A, B, C and D).


Lets you type an amplitude value for the loudness of the generated audio. Permitted values are between 0 (silence) and 1 (the maximum possible volume without clipping), with a default of 0.8.


Type (or use the keyboard arrows) to enter the required Duration. If the first digit you want is highlighted, just type the whole number. If the required first digit is not highlighted, use Left or Right arrow on your keyboard to move to the first digit, then type. You can also increment a highlighted digit with keyboard Up or Down arrow instead of typing.

  • When generating at the cursor, Duration initializes to 30.000 seconds (except for the DTMF generator which defaults to 1.000 second). However, your last entered Duration is always remembered.
  • When replacing a selection region, Duration always displays the exact duration of that selection to the nearest audio sample.

Tone/silence ratio

Use the slider to select the ratio between the length of each tone in the series and the length of the silences between them. This ratio is displayed underneath the slider as the "duty cycle" along with the resulting duration of each tone and silence. Changing the DTMF Duration changes the duration of each tone and silence while retaining the ratio between them.

For example, if you generate four tones in a sequence lasting four seconds, choosing a duty cycle of 50% in order to make the tones and silences of equal duration, the four tones and the three silences between them will all be 571 milliseconds long.


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