Episode: 1766
Title: HPR1766: Sox of Silence
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr1766/hpr1766.mp3
Transcribed: 2025-10-18 09:02:20

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This in HPR episode 1,766 entitled Sox on Silence, it is posted back in Fallen and in about
10 minutes long.
The summary is using SOX to speed up and remove Silence in a podcast.
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Hi everybody, my name is Ken Fallen and you're listening to Hacker Public Radio.
Today is a regular show by me and it's about SOX.
For those of you who don't know, SOX is a manipulation tool for audio and they call it
the Swiss Army Knife of Audio Processing Tools.
Now the ManPage is very complex, so I have to admit.
So I end up going to other how-to sites looking for people who have translated them.
We do use the SOX tool in the processing of shows on HPR, so therefore I've talked
about it a few times in the past and in fact I think I've also talked about this tool
a few times in the past, but it's been a while, so I updated it anyway today.
My podcasting workflow basically I want to squash as many podcasts as I possibly can
into my listening day and to do that I speed up the podcast.
That's nothing too fantastic, but I like to keep the pitch at the same.
So rather than people going chipmunk on you, have the pitch the same.
Just speed it off, have people talk faster and just speeding it up.
So I already had that.
One thing that I noticed though was that some of the podcasts I listened to, DLLTS,
tend to have long pauses in the podcasts where they go look something up.
Now what we do on the community news show or other shows, Mumble is brilliant for this,
is we use a tool in all dusty, cold, truncate silence.
It's under the effects menu, so you load your file in and you go truncate silence and
you can specify that after half a second of silence that you want to remove it.
So if there's ten minutes of silence, after half a second it will start removing that
and then it will truncate it down to half a second.
So if there's 15 minutes it'll be truncated to half a second.
So I was thinking, well this is bound to be available in SOX and indeed it is.
And I got a brilliant how-to on the digitalcardboard.com blog, 2009, 2008, 25, 4-day, dash, SOX, dash
of dash silence, link in the show notes for those who want to follow along.
Now basically what this does is it does the truncation of the sound.
So anything over 0.1 of a second it will truncate it down.
And I'm not going to go into the exact details of that command because I strongly advise
you to go to the link in the show notes where there are actual pictures about the piece
of audio track that year she was truncating and how to truncate the beginning and it's
example 4 actually trimming all silence that worked for me.
Just to give you an example of how effective it is, taking a random show from the internet
that was 1 hour and 43 minutes long, it truncates the silence and speeding it up the tempo
by 1.8, brings it down to 34 minutes, that's 1 hour and 43, down to 34 minutes.
So if you really want to have a look at that then the command line is in the show notes.
That's basically all I'm going to say now, I will give you an example of a random show
in the internet here, the before piece.
One time I had everything ready on time, and the equivalent after piece.
So that was it, admittedly you might find that a bit fast, so you can vary the speed
and you can also vary the amount of spaces that were in between if you wish.
So the command that I use is Sox, which is the Sox command line 2, that dash capital S to
show progress, dash low case V2 to show for both the warnings and that sort of thing,
and then I have the input file name and the output file name, and then I have another
V9 for some reason, I don't know why that's there, but anyway, tempo, it's the command
and then the speed which I have usually around 1.8 depending on the podcast I'm listening
to, some of them I don't remix speed operas load-on, then I have space remix, space dash,
which the dash converts it from whatever I get from stereo signals to a single audio,
so I can listen to one ear if necessary, handy if there are delays on the train and you
want to keep your ear up conductor commands, and then I just copied and pasted the command
from example 4 as I mentioned before, which is silent space 1, space 1 does 1, space 1%,
space dash 1, which is minus 1, space 0 does 1, space 1%, and that truncates the silence
nicely.
Thank you very much.
Okay, hopefully that was interesting as I say, I will whack this line into the show notes
for you and also include the before and after audio and a picture of the audio tracks
in Audacity.
Okay, thank you very much, tune in tomorrow for another exciting episode of Hacker Public
Radio.
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