Truncate Silence
From Audacity Manual
Truncate Silence automatically reduces the length of passages where the volume is below a set threshold level.
- Accessed by:
Throughout this description the words "silence" and "silent" mean sounds that are below the Threshold setting.
Min silence duration
Specifies the shortest allowable resulting silence. Truncate Silence will never shorten silent audio to less than than this length, and silent passages shorter than this length will not be altered. Default: 200 milliseconds. If the selection to be truncated begins with silence, that silence will be truncated to this minimum value.
Max silence duration
Specifies the longest allowable resulting silence. Setting this to the same as Min will therefore always reduce the silence to this length. Default: 1000 milliseconds.
Silence compression
A compression factor which proportionally reduces periods of silence that are longer than the minimum. This therefore has no effect unless Max exceeds Min. Default: 4:1, which compresses the silence in excess of min to a quarter of its original length.
Threshold for silence
Audio at or below this amplitude will be regarded as "silence", so will be truncated. Default: -40 dB.
Examples
- Simple usage: Setting both the Min and Max lengths to 5 milliseconds (ms) will truncate the silence to 5 ms. This is less than the length of a detectable silence, so will effectively eliminate it.
- Proportional truncation with compression factor: The resulting silence is calculated according to the following formula:
- (output silence length) = ((min) + ((input silence length) - min))/compression)
- with the constraint that output must be less than the maximum length.
So, setting the minimum to 33 ms and compression to 5:1, a silent passage 1033 ms long would be truncated to 233ms (33 + (1033-33/5)), unless the maximum was set to less than 233 ms. As a real world example, setting the minimum to 100 ms, the maximum to 5000 ms and the compression factor to 4:1 will have the effect of doubling the speed of a speech track with no pitch change, while keeping about the same cadence as the original.
Limitations
Truncate Silence only removes audio, it does not reduce or eliminate noise in the silent sections that it keeps.
Avoid using Truncate Silence on selections which have fade-outs or fade-ins. If you need to add fades, apply Truncate Silence before adding fades.
