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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 though about it a long time ago because I know we are using the same kind of technology in the airports.
Near the landing strips you can sometimes find some "sound reflectors" which just reflect the sound wave they receive from the planes. The sound is then cancelled by itself.
I saw it once in an airport in France and it works really well and costs next to nothing. AFAIK there's no sound wave modification in that system but I'm not sure (maybe the surface of the reflectors is made in a certain shape to change the sound wave a little).
But in this case it's different because the "box" must produce the counter sound wave. It's not just reflection, there is sound generation here. It means that the microphone and the speakers must be very precise or you just end up with more sound.
But if this guy can do it with 20 bucks it means that it's much easier than I though.
Iraq: war to save the U
Active Noise Cancellation stuff is a really cool technology. I wonder if this could be applied to cars and other "larger louder" things in the future.
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.
My laptop is so loud that if the fan(s) isn't/aren't running my roommate asks me if I turned it off. This thing generally has two fans running at times, and when it's really working hard, a third kicks in. My four year old desktop machine is much quieter than this thing.
Stupid HP. Had to go sticking a desktop chip in a laptop. Oh well, it still runs circles around my roommate's silent Centrino-based machine.
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.
can you take apart the cheap "noise cancelling" headsets and do it yourself? i would imagine all the parts and circuitry are there. lets see if my wife will miss her airplane headset....
Supreme executive power derives from a mandate from the masses, not from some farcical aquatic ceremony.
Well yes and no. Noise cancelling headsets are particularly effective because the ANC speaker and microphone are right next to your ears. This helps insure that the signal that arrives at your year can be sampled and inverted so that the sum cancels at the ear. It would be much harder to accomplish this with speakers and/or mics located away from the ear.
However, remote mics/speakers may work if the noise source is highly directional, like a waveguide (I suspect that's happening here). If you can effectively cancel the sound at the orifice, you'll probably achieve a significant reduction in transmitted sound, no matter the location of the receiver.
Damn funny post, irokitt.
One day a fan on your computer fails, and you never noticed, because you couldn't hear the squealing of the tortured bearings...
The interesting thing is with modern mobos (which control fan speed based on how hard the cpu is working/generating heat) you can actually tell to a point what's going on. I can set a compile going, go sit on the couch and read a book, and tell when it finishes (the cpu fan noise goes down and the hard drive noise goes up briefly - I run Gentoo where it writes the files at the end of the compile/emerge).
SB
It's old. The more humans I meet, the more I like my cats. At least they are honest.
You're forgetting that sound, being simply a pressure wave, travels a _lot_ slower than an electrical signal (6 orders of magnitude). If the mic is placed closer to the fan than the speakers, the speakers can have plenty of time to invert the signal and replay it. The distance is precisely chosen such that the speakers produce their noise simultaneously with the passing noise of the fan, even though it originated farther away. Delay's not a problem--no predicting needed.
I had an interesting idea based on this (I don't know if it's actually used). Fixing the distance and delay may not be accurate enough to match the signals completely, so you could have a second mic which listens _after_ the cancellation for beats. Superposition of the two similar waves produces the "beats" that musicians use to tune an instrument. By observing the frequency of the beats, the microprocessor could adjust the delay to more perfectly cancel the noise.
... just a new application.
;)
Before CPU's came along, this sort of thing used to be done with BBD (Bucket Bridge Delay) circuits, replaying the sampled sound 180 degrees out of phase. Of course, this only worked with single-frequency tones and the BBD had to be clocked at just the right correct frequency. Cancelling white noise (ie: fan whoosh) is a somewhat more difficult problem.
A number of "professional" aircraft pilot communications headsets have had active-cancelling (as in the article) built into earpieces (as opposed to the microphones) for several years, so as to reduce engine noise and pilot stress.
Car buffs here might even remember that VW had a Concept Car in the nineties which had an (I think) Bose-powered active-cancelling system in the cabin, the purpose being to cancel road noise and engine bay noise so you could replace it with sound samples of your favourite sports cars: Ferrari's, Porsche's, etc. Not sure it ever took off, though.
My acoustics book said that if you put a person with normal hearing into a sound isolated anechoic chamber, and give them awhile to adjust, they will actually hear the blood flowing in their ear.
Point being is that it would be completely pointless for them to be any more sensitive. Quite amazing really.
Why do I have this? I don't smoke.
Seperating audiophiles and thier money is like shooting fish in a barrel. I think there is a lot of placebo effect in high end audio. You just paid 800 bucks for a few meters of cable. It was a multi-thousand dollar system before the new cables. Do you think it could sound bad now?
I'm lucky. I have very good hearing, but I'm pretty tone deaf. The medium priced stuff at Best Buy sounds just as good to me as the high end stuff at the specialty stores. There's no point for me to shell out the cash.
-B
My acoustics book said that if you put a person with normal hearing into a sound isolated anechoic chamber, and give them awhile to adjust, they will actually hear the blood flowing in their ear.
An even cheaper demonstration is to simply plug your ears. It works better in an area that's already quiet, but if you simply plug your ears with your fingers, you'll hear the blood flowing in your veins and arteries. That's what that low, rumbling noise is that you'll hear.
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