Computers / Noise & Silence

I have a question that has been bugging me for a while now. As you know the sound waves can cancel each other out if they are out
of phase see hire:

en.wikipedia.org/wiki/Interference - Contents - # 4 Constructive and destructive interference

The noise is a noise, it does not change, so Why wont ppl record the noise that comes from inside the Desktop PC`s & make a device that will output the same waves, olny in 180° out
of phase ? would not the PC`s be silent then?

See image below, cuz the fkin forum wont allow me to post a link...
astro-canada.ca/_en/_illustrations/a4313_interference_en_g.jpg

That's how noise cancelling headphones work. If you can figure out a way to cancel out the sound of rushing air from the fans by all means, make it and market it, and you can become rich.

This what the wiki says: en.wikipedia.org/wiki/Noise-cancelling_headphone

Noise-canceling headphones have several limitations:
They work well for sounds that are continuous, such as the hum of a refrigerator or the sound in an airplane cabin, but are rather ineffective against speech or other rapidly changing audio signals.

So according to this info, there should not be any problems making this kind of devices for Pc`s to eliminate unwanted noise. Noise-cancelling headphones start from around $50 USD, So why don`t they make them for PC`s?

Well probably because computers aren't THAT loud if they're taken care of the right way. But, I mean try and experiment, some things still haven't been invented, and you never know you could develop and market this to become a billionare!!

EDIT: UBER STEAL! *steals idea*

Also, headphones are much easier to work with, since it's almost like dealing with a closed system. The output of the speaker, including the mirrored waves from the microphone on the outside are played into your ear which is small and in 1 spot. With a whole PC, you'll need a large speaker to playback the inverse waves, but then how do you deal with the microphone feedback? Also, there are an infinite amount of positions you could stand relative to the case, whereas headphones can only go one way.

I second that.

I'm a student at a university which had a team researching a system to cancel noise from shooting ranges. I'm not sure if they're still researching it or if they gave up. In an open space it is very difficult to create a system which would cancel the noise everywhere.

In the room where your computer is, there probably are many surfaces that reflect and absorb the sound, which makes everything quite complicated. Since the sound from the fan and the cancelling sound from your speaker come from different locations, they meet the surface in a different angle. This means that there are a lot of waves present: the original sound and anti-sound waves, and a billion reflected waves. I guess that you'd get spots where it's silent, spots where it's just as bad as it was before, and spots where it's worse than before.

a real time mic inside the case and outputting to a second "PC/case speaker" should at least help reduce it...

damn too bad i have no knowledge to experiment with it like what would happen if we glue foil inside the case & try to cancel out sound wouldnt this rise the success % ? Or how about a bit different approach?

A vacuum case? As we know the sound only moves through the air. Yes we need air to cool the insides so we make only vacuum case plates, they should be really easy to make & this should reduce the sound a lot. I came to this conclusion because when I removed the case from my PC the noise got bigger. Also to make the noise even smaller we can put a cloth as a filter in front of other leftover holes.

The Question is how we can pump out the air? or do the so called sound proof materials for PC cases really work?