It may be easier to buy quieter fans, but it could be more fun to try the following:
http://www.analog.com/library/analogDialogue/archives/34-02/noise/ Matthew ----- Original Message ----- From: "Maarten de Boer" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Thursday, April 04, 2002 2:46 AM Subject: [linux-audio-dev] sound cancelation with anti-sound > 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 > > > > >
