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
