Silence finder

Audacity Help Forum Windows
1

Hello,

OS:windows 7
audacity version:2.0.3

How silence finder can identify silence in media file?
What is the actually functionality of silence finder to find silence in media file?
Is there any source file in audacity source code?

2

Silence Finder is a Nyquist plug-in http://wiki.audacityteam.org/wiki/Nyquist_Plug-ins_Reference
Nyquist plug-ins are written in plain text.
You can view the Silence Finder file here: http://code.google.com/p/audacity/source/browse/audacity-src/trunk/plug-ins/SilenceMarker.ny

3

Thank you steve,

How silence finder can detect silence or data?
suppose a media(.mp3) file is playing,how it can find silence?
for example by measuring it’s amplitude or intensity or any other factor.

4

Silence Finder is not used during playback - you have to apply it to selected audio (like using an effect). http://manual.audacityteam.org/o/man/silence_finder_and_sound_finder.html#silence
Silence looks at the peak level of the selected audio and if that level remains below the Threshold (first control) for longer than a set time period (second control) then it is classed as “Silence” and a label is created and positioned according to the setting of the third control.

5

Is it possible to measure silence by sample, not by threshold value?

In silence marker source code,I found that
they are converting the silence duration in seconds to length of samples.

but i can’t understand that formula…which is as below

(setq sil-length ( sil-dur s1-srate))*

6

I’m not sure exactly what you mean.
The “Sample Data Export” tool in the Analyze menu will print out sample values: http://manual.audacityteam.org/o/man/sample_data_export.html


“sample rate” is the number of sample in each second of audio. Thus you can convert between “number of samples” and “duration in seconds” by the simple formula:
(number of samples) = (duration in seconds) x (sample rate)
or the other way round:
(duration in seconds) = (number of samples) / (sample rate)

In the case of Silence Finder, to speed up processing, the audio has been resampled to a lower sample rate (less samples per second, hence less samples to analyze).
The sample rate of this “low sample rate copy” has been given to the variable “s1-srate”.
Using the same formula as above, the duration in seconds can be calculated by multiplying the duration in seconds, by the sample rate.

7

Thank you steve,
given information is very helpful for me.