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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.
When my CPU fan starts to make noise, I just whack my case until it stops.
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.
Installing a Zalman HSF is exactly what I did. Highly recommended. Or (and), you can just buy a fan controller for the money (or both) to really quiet down your system.
Where this would be really useful is for the whine of hard drives. It would be far better than the current system of enclosing it in some casing thus making it run even hotter.
Once you silence my CPU, you'll hear my hard drive. After you silence my hard drive, contend with my video card cooler. Quiet my video card cooler, and hear all 4 of my case fans instead. Quiet those, and hear the active cooler on my northbridge. Shut that up, and I'll go mad with all the silence...
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Of course he is much smarter than I am, otherwise I wouldn't be posting on slashdot.
;)
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In most offices, they don't use noise generators (ie Gossip Support Group) to cancel out talking noises, instead they put in a lot of plants, cubicles, which act to absorb most of the noises.
If the noise is pointing at your directly, then you probably need a cancelling method. If it is a general-direction noise, it should be absorbed rather than trying to cancel it (where you need to find it in the first place).
Rock that crushes, Paper & Scissors that don't matter.
I wonder what would happen if you placed some huge speakers in a room connected to mic's and some noise cancelling gubbins....would everything just fall silent no matter how loud you shouted?
Could be a useful mute tool for the girlfriend when she goes on too long:
GOD, you're so inconsiderate, you never take my feelings into acco
*click*..........
Not to worry, the cancellation -can be- that complete. In practice, there will be some residual noise, but it will be very quiet.
Most car noise these days is not from the engine running. Technology these days allows new cars to run incredibly quiet. Probably 99% of the noise you hear while traveling down the highway is road noise. Noise produced from your rubber tires against pavement. I saw a news flash a couple years ago about a new type of pavement that dramatically reduces that noise, but it's too expensive to be widely used.
All this does is allow PC makers to get away with making hotter and noisier systems. We should be pressuring the industry to be cooler and more efficient.
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".
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.
I own a set of noise cancelling headphones and there is no perceptible noise being emmitted from them to the outside world. The noise cancellation circuitry takes the incoming signal and inverts it to cancel out the original incoming sound wave. Conservation of energy doesn't really apply. You aren't really destroying the energy of the sound waves, just cancelling it. Energy is spent on both the positive and negative signal. Although I just minored in acoustics so I'm probably missing something. Any professional opinion is appreciated.
Well, I do have a PhD in physics, but I should bow to your actual experience with the device
My guess is that the sound coming into your ears is only a tiny amount of power, so reradiating that power in all directions doesn't make any amount of sound that would be perceptible to someone a significant distance away. Your eardrums only have a surface area of a few square mm, the the amount of energy impinging on them is normally only a gazillionth of a watt. Your ears are amazingly sensitive devices.
Conservation of energy doesn't really apply.
I was obviously wrong in my prediction about an audible noise for people not wearing the headphones, but I'll bet both my testicles that it's not because conservation of energy is violated. You'd get the Nobel Prize if you found a violation of conservation of energy.
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...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
If you reverse the wires, it sounds like a V20.
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.