I'm such a nut about making my PC quieter, that I'm seriously researching noise cancellation.

In theory, I could capture the annoying PC noise. Then invert it using an audio editor, then play that inverted noise out the PC's speakers.

Problems encountered... the speakers obviously don't emit the sound from the same spot the PC makes it's noise. Secondly, that cancellation sound needs to be constantly emitted, as long as the PC is on. I can get the sound to loop, but there's a small (and very obvious) delay between plays. Then, of course, I want to be able to add my CD, MP3, etc, computer sounds on top of that cancelling sound... in real time. My old sound blaster card can mix several sourced, so that problem is my least.

Anyone else interested? Since the PC's sound is fairly constant, it should be very doable.

Dave