Truncate Silence

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Peter 25Mar14: the GUI here appears not to be consistent with other effects in Audacity. In other effects the units if a control are written encased in round brackets (though occasionally in square brackets) immediately after the control and before the data entry box; examples are Amplify and Bass and Treble. I'm not sure if this is something we have to worry about - in this case it may look better the way Steve has it now with the units after the data entry boxes. For me it does make the documentation here look a little clumsier than the other effects.
  • Steve 25March14: We have examples of units in brackets before the control, and not in brackets after the value (for example, Change Pitch, Classic Filter, Compressor, Normalize).
    • If the units are before the control then round brackets should be used. I think the only use of units in square brackets are a few old Nyquist plug-ins (that need updating).
    • My understanding is that units may be before or after the controls as appropriate. In this specific case it has been suggested that at some point there may be an option for time units in seconds or milliseconds. That would be much easier to add with the units after the control as it would avoid changing the layout.
    • Also I think that (in this case) "Truncate to: .... seconds" in the interface is a bit easier for users than "Truncate to (seconds): ....", and looks better imo.
      • Gale 25Mar14: Preferences are inconsistent too - compare the Playback Preferences and Recording Preferences (after the text box) with Spectrograms Preferences (before the text box). I think units after a text box is better, but feel we should not do a mix of before and after. If there is a text box followed by a slider as in Bass and Treble, units before the text box make a little more sense, but perhaps not enough to outweigh being consistent.
    • The "dB" after the "Level" control is superfluous - do we want to remove that?
  • Peter 25Mar14: Well I think we should either remove the "dB" text after the control - or remove it from the values in the control. Which is more consistent with other effects?
    • Steve 25March14: The multi-choice dB menu is currently only used in two effects, Leveler and Truncate Silence, and the code is common to both. I quite like the multi-choice in this effect as it makes it more difficult to set it badly wrong. I suggest that we remove "dB" text that comes after the control. Any objections/agreement?
      • Peter 25Mar14: I'm happy just to have the text removed that comes after the control.
      • Gale 26Mar14: +1 on the whole. I think to have only numbers in the drop-down would look worse, unless we had a less narrow drop-down as in Classic Filters. If we did that, it might suggest right-aligning the drop-down here to be close to the unit, which would then contradict the left-align in Classic Filters.

FrenchFlagSmall.png Truncado de silencio


Truncate Silence automatically reduces the length of passages where the volume is at or below a specified level.
  • Silences are detected that remain at or below the specified level for at least the specified length of time.
  • The detected silences are then made shorter by automatically deleting a section from the middle of the silent region.
  • For the purposes of this effect, the words "silence" and "silent" mean sounds that are below the detection level.
  • "Detected silences" mean sounds that are below the detection level for at least the specified length of time.
Accessed by: Effect > Truncate Silence...
Truncate Silence dialog

Operation Mode

There are two methods available for shortening the silence. The simplest method is by truncating the silence (default mode) and a more advanced method is by compressing the length of the silence.

Truncate Detected Silence

When this method is selected, silences are simply shortened to the specified duration (see example below).

When this option is selected, the "Truncate to:" (seconds) control is available lower down the interface and the "Compress to:" (percent) control is grayed out. All detected silences are shortened to the same duration.

Compress Excess Silence

This is a more advanced mode that allows silences to be shortened proportionally according to their original duration.

When this method is selected, silence in excess of the specified duration is reduced to a percentage of its original duration (see example below).

When this option is selected, the "Compress to:" (percent) control is available lower down the interface and the "Truncate to:" (seconds) control is grayed out. Because silences are reduced by a specified percentage the final duration of each detected silence varies according to its original length.

Detecting Silences

There are two controls that determine which audio will be treated as "silence":

  1. Level (dB): to be treated as silence, the audio must be at, or below this level.
  2. Duration (seconds): to be treated as silence, the audio must remain below the specified level for at least this amount of time; this value must be at least 0.001 seconds.

Reducing the length of detected silences

There are two controls that determine how much silence is removed, and hence the final length of each silence. Only one of these controls is available at a time, depending on whether the simple Truncate Detected Silence or the advanced Compress Excess Silence mode has been selected.

  • Truncate to (seconds): when the audio remains below the specified level for at least the specified duration, it will be reduced to this duration.
  • Compress to (percent): when the audio remains below the specified level for at least the specified duration, the excess silence is reduced. That is, if the original silence is 10 seconds longer than the specified minimum, then there is 10 seconds of excess silence. The percentage refers to this 'excess' silence, and not the entire detected silence.

Examples

Truncate Detected Silence examples:

Shorten all silences that are longer than 2 seconds to 2 seconds

This may be useful for shortening inter-track gaps from an LP or cassette recording.

  1. Set the Operation mode in the drop-down to "Truncate Detected Silence"
  2. Set the detection "Level:" control. If there is noticeable background noise you may need to set this as a higher (less negative) value than the default.
  3. Set the detection "Duration:" control to 2 seconds. Silences of 2 seconds or more will be chosen by the effect for truncation.
  4. Set the "Truncate to:" control to 2 seconds. All detected silences will be truncated to 2 seconds.
  5. Click OK

Shorten silences that are longer than 20 seconds to 5 seconds

This may be useful for removing long pauses in a speech recording, without affecting the natural rhythm of the speech.

  1. Set the Operation mode in the drop-down to "Truncate Detected Silence"
  2. Set the detection "Level:" control.
  3. Set the detection "Duration:" control to 20 seconds. Silences of 20 seconds or more will be chosen by the effect for truncation.
  4. Set the "Truncate to:" control to 5 seconds. Silences of 20 seconds or more will be truncated to 5 seconds. Silences of less than 20 seconds will remain unchanged.
  5. Click OK

Peter: commenting out this section for now until an example is provided.

Compress Excess Silence example

To be provided.


Limitations

Truncate Silence only removes audio, it does not reduce or eliminate noise in the silent sections that it keeps.

Warning icon Avoid using Truncate Silence on selections which have fade outs or fade ins, since it may remove the quietest part of fades. If you need to add fades, apply Truncate Silence before adding fades.


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