Anti-Noise?

What I wonder is why they don’t make an anti-sound device to cancel the
noise of the fans. This technology is well-known, simple, reliable and good
at dealing with repetitive sounds (like fans I would guess). It’s been used
in cars, I’ve seen a Lotus on TV that had this technology built in.

For the PC it could be made as a PCI card or in another format. Has anyone
seen a product like this? Do they know what it would cost? Does anyone know
who to contact to get these into production? After all, we don’t care how
many fans or how much noise as long as we don’t hear the noise.

I asked a friend who has a ton of audio and electronics experience about this, and
he was very skeptical about the feasibility of this at a reasonable price.

Basically, he said that in order to such devices to work, the “anti-noise” has to
be in perfect inverse phase with the noise. Otherwise, you just end up with two noises.

PCs make a varieties of noises, and not all constantly. For instance, hard drives make sporadic noises. As noise patterns
change, any generation device would have to sense and instantly change the anti-noise waveforms. This takes a lot of
computing power.

Sonically, you have noise coming from fans, hard drives, etc., bouncing around all over
the case, so just moving around a little can yield different noises.

A good example of this would be the computer in the bedroom. The noise pattern you’d have
sitting in your desk would be different than the one you’d get lying in bed. You would need
to have sensors to pick up whatever the sounds were in a specific location to calculate countermeasures.

Afraid that’s undoable for the price of a typical PCI card.

Email Ed