Tech Blog

Removing silence from audio using sox

Posted At : November 25, 2009 11:11 AM

I've had a look at this a few times before and each time I've gotten a little bit further and then gotten frustrated and failed.

However, this time I finally managed to get past all the hurdles and jump through all the hoops to make this work.

Audio before and after

Scenario is a follows. Audio file is comes in in alaw or ulaw format and we want to trim any silence before and after it.

First step is to convert it from alaw to pcm encoded wav file as SOX has issues filtering silence in alaw files

sox -t alaw in.alaw -c1 -2 -r8000 -e signed-integer temp.wav

Then we do the trimming in one fell swoop.

sox temp.wav out.wav silence 1 0.1 0.1% reverse silence 1 0.1 0.1% reverse

A huge thanks to this article for giving such a thorough overview of the how silence detection works in sox.

Too easy, when you know how :-)