[pulseaudio-discuss] Reducing ambient noise from Input devices?

Alexander E. Patrakov patrakov at gmail.com
Tue Mar 3 23:46:41 PST 2015

04.03.2015 07:18, Kai Hendry wrote:
> Hi there,
> I made a recording that hopefully demonstrates the issue I have with
> my voice recordings:
> http://r2d2.webconverger.org/2015-03-04/microphone-test.mp4
> 1. Apple headphones
> 2. X1 Carbon 3 internal mic (sounds best atm)
> 3. http://www.smartlav.com/ (sounds fantastic when recording from my iphone)
> I made the recording via ffmpeg
> https://github.com/kaihendry/recordmydesktop2.0/blob/master/x11capture
> First issue is auto-levelling. Can pulseadio do that at all? It's
> quite frustrating to monitor the levels in pavucontrol...
> Second more pressing issue is the amount of noise via the attached
> microphone inputs. Why is there so much?! Are there tricks to reduce
> the ambient noise? Google's best result is
> http://askubuntu.com/questions/421671/microphone-static-background-noise-suppression
> and I did try that previously with my X220 to no better results &
> setup is VERY finicky.
> IIRC both Windows & MacOSX have "Ambient noise reduction" recording
> options built into their native audio system, therefore is it
> reasonable for me to file a bug on pulseaudio to match this?
> Many thanks for any tips to improve the voice recordings in advance,

Both auto-levelling and noise reduction are done by module-echo-cancel. 
However, it works only when something is being played through it. So, it 
really works only for VoIP apps, but not for recorders.

So, the procedure to use it in your scenario would be:

1. pacmd load-module module-echo-cancel   # possibly with source_master 
and sink_master arguments referring to the correct sound card, if you 
have more than one
2. aplay -f dat /dev/zero
3. Using pavucontrol, move the stream of aplay to the echo-cancelled sink
4. Start recording
5. Move the recording stream to the echo-cancelled source using pacucontrol.

There is no need to file a bug, because it already exists: 

Alexander E. Patrakov

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