Subject: [linux-audio-dev] sound cancelation with anti-sound
From: Maarten de Boer (mdeboer_AT_iua.upf.es)
Date: Thu Apr 04 2002 - 13:46:58 EEST
i have been thinking about the following before, and now
that i read about it on slashdot, and it got me thinking
a bit more.
the issue is sound cancelation. the article mentioned
on slashdot,
http://www.newscientist.com/news/news.jsp?id=ns99992094
talks about a (very expensive) general approach of
removing sound with anti-sound.
personally, i am more interested in a very specific
noise: the noise of the cooling fans in my pc.
i am sure it would be possible to have a background
application running that uses the soundcard (could be
a cheap one) to do this. the sound of each fan has
almost constant pitch, and i suppose it is harmonic.
the application should record the noise, analyse it:
determine the pitch of each fan and seperate the sounds
of all fans, invert each signal, and play it back.
this should work reasonably well as long as the pitch
doesn't change. by reanalising constantly, any changes
in the sampled signal have the be analyses and added
to the canceling inverted signal.
the problem is the sound seperation. The application
should be low on CPU usage, so I guess time domain
processing is the only option. but we are talking about
let's say 3 different signals with rather simple content...
any suggestions / remarks?
maarten
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