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Cancelling Out CPU Fan Noise
Percy_Blakeney writes "After realizing how noisy his computer was, a professor at BYU has created a new CPU fan that uses small microphones and speakers to cancel out its own noise. It isn't perfected yet -- it only nixes the whine, not the whoosh -- but it looks like it could be promising, especially given the professor's background: making jet engines quieter."
I have heard of something like that for cars ages ago, basically replays the engine sound over the car sound to negate it.
There were various addons with such a system so you could add a roar of a 911 or rattle of a clapped out sad wanker boy racer in the car.
Jonty! Neil! Work!!
Its actually used on some heavy earthmovers and tractors simply because its actually cheaper than making a decent muffler.
Don't worry - its just stigmata. Pass me a napkin and don't you dare tell my mother.
What you describe is not that same thing which is mentioned in that article. You describe passive cancellation (i.e. simply reflecting and hoping it will cancel the original noise), whereas the article describes active cancellation (i.e. recording the noise, computing the negating and sending it off) of noise.
Not to worry, the cancellation -can be- that complete. In practice, there will be some residual noise, but it will be very quiet.
If you can't hear it, it's not hurting you (assuming that it's a frequency that you could normally hear). Typically what will happen with a scheme like this is that the cancellation will only work in one direction. In other directions, it will reinforce rather than cancelling. For instance, you can buy noise-cancelling headphones, but the cancellation only works for your own ears, which gets the sound in just right right phase; to the people around you, there will be a perceptible noise coming from your headphones! Conservation of energy says you can't just destroy the energy of those sound waves. Most likely you're just sending extra-strength sounds waves somewhere else. Theoretically the extra energy could be converted into heat, or electrical energy, but I doubt that's really practical.
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No Slashdot post about computer noise is complete without a link to Silent PC Review.
Losers choose to abuse the use of "loose".
...is to buy Zalman components ( http://www.zalman.co.kr/english/intro.htm )
I built my last PC with their components. When I powered up for the first time I freaked out because I saw the power light go on, but that was it. Then the BIOS came up, thank god. No noise at all...seriously. I mean, I expected quiet, but not noiseless...
I was extremely let down by my hard drive though. Considering Seagate had a great reputation for quiet hard drives, I figured I'd get a Seagate SATA hard drive...well their SATA drives are loud as heck when writing...
01100111 01100101 01110100 00100000 01101111 01110101 01110100 00100000 01101101 01101111 01110010 01100101 00101110
The fan controller in the Power Mac G5 is aware of the noise amplifying and canceling effects of running different fans at different speeds in different combinations. It actively uses this information and uses it in decisions on how to cool the G5 in the quietest manner using the 9 strategically placed fans.