[LAU] denoising audio files

Julien Claassen julien at mail.upb.de
Mon May 21 10:14:49 UTC 2012

Hi Iain!
   You should be able to handle that in Linux. Seeing, that it's traffic noise, 
a typical fft-based denoising tool is out. Your tools of choice should be EQ 
and filters.
   You can of course remove the very low end regardless. You could try to find 
the bass frequency of the voice and set the low end even higher than 50Hz, not 
too close though, since no filter is perfect.
   Then put an EQ on your recording, Activate only one band, set it as narrow 
as possible and the gain about 12Db or even higher. Then sweep the bands 
frequency slowly. You will find the first point where it hurts. Just lower the 
gain drastically below 0Db.
   Another idea: If it's a stereo recording with the voice bang centre, you 
might perhaps go a stranger route. There was a sort of karaoke LADSPA plugin, 
which tried to lower something in the centre and only leave the rest. If that 
works, leaving mostly the traffic, you can use some graphical wave-editor or 
display to line the two files up, in case, that there is some delay introduced 
by the plugin. that done, you can use csound, PD or some other allround synth 
to subtract the mainly traffic only signal from the original. This is an 
outside chance, but it may end up giving a good result.
   Kind regards

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