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 should have patented it...

[zeux]

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.

Re:I should have patented it...

[Anonymous Coward]

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.

Re:I should have patented it...

[Martin Blank]

I have a question about active cancellation, as I've heard of it being used in other places. Does the cancellation of a noise of a given frequency have any potentially harmful effects that become less obvious through cancellation? For example, does a high-pitch tone that could cause hearing loss over time become more dangerous now that there are two high-pitch tones (albeit directly off-phase) now sounding, or is the cancellation that complete?

Re:I should have patented it...

[fireweaver]

Not to worry, the cancellation -can be- that complete. In practice, there will be some residual noise, but it will be very quiet.

Re:I should have patented it...

[tiger99]

No, the cancellation can only be partial and in certain positions. The problem is simply a matter of time delay, the speed of sound is not very high so for practical dimensions there is substantial phase shift. By using a lot of speakers and very complicated processing, you can make it better, but it is still in the form of an interference pattern, and will always show peaks in certain places. You would need to make the summation of the speakers look like the original source, but in antiphase, to everyone around, to get cancellation. The wavelength of sound at 1KHz is about a foot, if you use one speaker you need to get the difference in disatnce between everyone and the speaker very much less than 1 foot so they all see cancellation. The idea is to put the maxima where they do least harm. These systems only work on regular frequencies, you can't predict random noise, and so can't cancel it unless maybe the speakers are all very much nearer people than the original source so there is time to do the computation.

A very greatly hyped and over-rated technology, which in some specific circumstances will provide a useful reduction (10dB?) in low-frequency noise, for example in the Dash8-Q400 aircraft, where propeller blade fundamental frequency noise is at 85Hz in the cruise (6 blades at 850 rpm, which is lower than most), and where people tend to sit in predictable places, it does quite well, although a fair part of the reduction is by trimming the relative phases of the two propellers (which should run in synchronism in steady flight, although this is not a safety-related function and might not always work, as it is not provided with any backup system), how that compares to the contribution from the speakers I don't know. The active noise suppression system can command the propeller controls to adjust the phasing, and indeed select which blades to synchronise, as they might be slightly unequal, of course it has only extremely limited control authority to avoid it becoming safety-critical, so it can only trim the relative angles very slowly. That is basically adjusting two noise sources so they make the least overall noise, inside the aircraft. I always had the suspicion that at certain precise positions outside (as presumaly happens with all twin-engined aircraft), the noise would be doubled, but it passed certification so it must have been acceptable. Probably much quieter than the average jet, Avro 146 excluded, anyway.

At 85Hz, the wavelength is about 12 feet, so the problem is somewhat simpler, but still very complex....

I am not a noise expert, but I can clain very intimate knowledge of the propeller sync system, called "syncrophase" in this case, being one of its main hardware designers. The propellers are synchronised at the desired angle, within about quarter of a degree, which is not bad considering there is no mechanical connection, the engine power is several thousand horsepower, and only a little pulse as each blade passes a sensor gets sent from the master controller to the slave. Oh! sorry, I forgot, can't use these words any more..... Back to the drawing board. Ground the aircraft in the interests of political correctness. Now, did it have any IDE drives on board?

On a jet, by comparison, the fundamental frequency is much greater, and the engines can't be synchronised anyway, so these systems are not worth bothering with.

Re:I should have patented it...

[bcrowell]

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.

Re:I should have patented it...

[Cosmic_Hippo]

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.

Re:I should have patented it...

[bcrowell]

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.

Re:I should have patented it...

[Cosmic_Hippo]

Heh, I hope I wasn't implying that conservation of energy was being violated. I just though that destruction of energy and cancellation of the signal were different in this case. I think I worded it wrong. No testicles need to be wagered :-)
The experience I've had with the equipment in class showed that the noise cancellation circuitry recorded the original sound wave, inverted it and fed it back into the speaker. The combination of positive and negative voltage basically told the speaker to output zero signal for that particular frequency. Nothing is destroyed, it's more like an electronic tug-of-war. It makes listening to music a lot more enjoyable, however it works.
Thanks for the reply.

Re:I should have patented it...

[FallLine]

Well I'm no PhD in physics, but I (did stay at the holiday inn express last night^H^H^H^H^H^H^H^H^H) do own a QuietComfort2 headphone set. I would agree that there is no discernible noise coming from outside the earphones. I suspect the explanation though is relatively very simple (or perhaps I'm just naive). The earphone cup is already quite muffled. The noise cancelling circuity only needs to "cancel out" a tiny amount of noise, that which would reach your ear by leaking through the insulation. Whatever noise is created by the cancellation speaker is quiet relative to outside background noise and will be further muffled by the headset before someone sitting next to you can hear it. In other words, whatever background noise you'd hear without the headphones is almost certainly (in real world applications) going to be orders of magnitude louder to a neighbooring passenger than the noise coming through your earphones.

This is why they havent gotten rid of the "whoosh"

[Ayanami Rei]

The whine of the fan is due to vibrations caused by the inefficiency of the particular design, and manufacturing defects in the fan or it's mounting. A "perfect" fan would be silent except for the sound of moving air.

They haven't gotten rid of the whoosh sound yet; canceling out the whine while still leaving the sound of moving air is probably a good sign that air is still moving :-) If the managed to someone completely mask the sound, then I'd start worrying about air flow reduction (although I'd start by

Re:I should have patented it...

[sjames]

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.

Your bloodline is safe :-) I'm guessing the energy is dissipated as heat in the speakers and voicecoils themselves. The cone will travel further than normal since it will be 'flowing with' the incoming pressure waves rather than working against the air as normal.

As you say, there's only a small amount of power in the small zone where the sound is deadened, so not all that much extra heat in the speakers.

Ears are sensitive indeed!

[chadjg]

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.

Re:Ears are sensitive indeed!

[ziggy_zero]

It should be noted that the flow of blood, chewing, other internal sounds, etc. would be a LOT louder if we didn't have the middle ear. One of its (theoretical) functions is to reduce the transmission of bone-conducted sound to the cochlea.

/trying to see if I can actually interject something I learned in my music psychology class into a conversation....

Re:Ears are sensitive indeed!

[TwistedGreen]

The logical next step, then, is to evolve quieter blood!

A Cheaper Way

[Kombat]

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.

Re:I should have patented it...

[xtal]

You'd get the Nobel Prize if you found a violation of conservation of energy.

Not mine, but.. compelling.

Casimir Effect [wikipedia.org]

Nope

[Sycraft-fu]

Sound is a wave, specifically a compression wave. It is fluctations of air pressure, which your ear interprets. You can see this in how speakers work. They vibrate back and forth to produce compression and expansion waves. Well, as with all wave dynamics, if you hit a wave with it's opposite, it cancels. Quite simple to think of why with sound. You have a high pressure peak and an equal low pressure peak that collide. The net effect is zero pressure (in relation to ambient atmospheric pressure).

Now if you screw it up and don't time it right, yes, you could increase the sound. However provided your system is indeed doing it's job and producing opposite waves in correct time alignment, it cancels out.

Try it yourself some time. Take two identicle speakers and feed them both the same sound (as in one mono sound to both channels, not a single stereo source). Reverse the polairty on one speaker (plug the black plug into the red and vice versa). If you have them setup normally and listen to the sound far away, it'll simply sound defocused, as though it has no apparent centre or source. This is a good way to focus your speakers, the more defocused an out of phase sound is, the more in focus an in phase sound is. However now take them, get them right next to each other, and point them at eachother. You'll hear almost nothing. PRetty much all you hear is the sound that radiates from the cabinets.

I use this trick when I'm burning in speakers. New speakers come from the factory with everything a little tight, as everything does new. Over the first month of playing they slightly change their sound as they get to their normal "burned in" point. It reach it quicker, you can just pump some white noise through your speakers. Well loud white noise is likely to piss off the neighbours, so I invert one speaker and have them face each other. Reduces it to a pretty minimal level and gives the speakers the desired workout.

Re:Nope

[Sycraft-fu]

1-2dB at certian frequencies (yes, at the limit of what you can hear different) and with a studio dB metre/spectrum anaylizer (don't remember the brand). It was in a studio, under ground, climate controlled, in the desert in the summer, so fairly consistent conditions.

Also, it eliminates the smell. New B&W speakers produce an odd smell when you shake the air up in them (ie whenever there is any significant amount of bass). Do it enough and for long enough, it goes away.

This solves that and will break

Re:Nope

[Ralph Wiggam]

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

Re:Nope

[BlueJay465]

Listening to the differences in the different types of speakers and monitors working at a Guitar Center over the holidays, I was blown away by the sound quality of some of the studio monitors in their Pro-Audio department, and then comparing them to the high-end home-theater gear at the Magnolia Hi-fi just down the street.

You will get a lot more bang for your buck with a good set of monitors while only taking fraction of the space. Check out the Event TR [event1.com] series or M-Audio [m-audio.com]'s line. Most decent music equipm

Re:I should have patented it...

[Reverberant]

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 canceled by itself.

I think you're referring to a "blast fence." Those have nothing to do with active sound cancellation, they're strictly passive noise control devices that block the path between the noise source and the receiver (just like highway noise barriers). See here [blastwall.com] or here [hmmh.com] for examples (the latter is a run-up enclosure, but it's the same principle).

Prior art? 'rev'

[janbjurstrom]

$ echo 'I CANT HEAR YOU' | rev
UOY RAEH TNAC I

Ah, the silence :)

I have a better and cheaper solution...

[Scratch-O-Matic]

I've constructed a simple device that cancels almost all noise from my fan. A common #2 pencil inserted into the fan blades does the trick quite nicely. I've used this system sucessfully on three different computers, and I can tell you that the noise reduction is dramatic. Oddly, all three of them stopped working within minutes due to unrelated problems.

Re:I should have patented it...

[zeux]

Of course he is much smarter than I am, otherwise I wouldn't be posting on slashdot.

And I'm French, remember ;)

Re:I should have patented it...

[Cecil]

BYU is prestigious? It looks to me like a religious school tightly associated with the Church of Latter Day Saints, and I would personally consider any research that comes out of it a little bit suspect. But maybe that's just me. Do they have a good history of acclaimed scientific pursuits?

Wow

[michaelhood]

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.

Re:Wow

[crackshoe]

Its actually used on some heavy earthmovers and tractors simply because its actually cheaper than making a decent muffler.

Re:Wow

[Martin Blank]

Maybe on the inside. On the outside, they're already quiet enough that I miss when they're coming up behind me.

Damned cars always trying to stalk and eat me.

Re:Wow

[SEWilco]

Excuse me, what did you say?

Re:Wow

[krosk]

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.

Mod up!

[Ayanami Rei]

We're currently doing experiments monitoring this at work. We want to isolate engine vs. tire vs. transmission noise across various makes and models of cars during ramp up, idle, and braking. It's a fun project involving lots of wireless and embedded tech, with audio, sig proc, and linux thrown in there too to make it interesting.

From what little of the results I've looked at, it's pretty clear that tire noise is dominant during cruise.

Re:Wow

[afidel]

But in this case it's absolutly retarded. For only $17 MSRP you can get the Arctic Cooling Silencer64 which is designed to handle any AMD Opteron/Athlon64 currently shipped and produces only 20dB of noise (essentially silent). It achieves this through a large, slow fan which also has the advantage of being more reliable =)

Re:Wow

[Cornelius the Great]

"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."

The 2003 Dodge Viper SRT/10 has side exhaust with active noise cancellation. It can be switched on/off to allow for "stealth mode" or a throaty sound- though I can't imagine why... I love the sound of a V-10.

Re:Wow

[RabidOverYou]

If you reverse the wires, it sounds like a V20.

Re:Wow

[Genda]

Actually it has been used in a variety of applications for some time. Back in the 70s a huge diesel generator had mikes place on it, then further out was surrounded by large speakers. The mikes picked up the motors full spectrum and the speakers played it back at the motor. There were two marked effect;
1. The generation room went from deafening to almost whisper quiet...
2. The motor efficiency jump markedly. It seems that one of the significant causes of mechanical inefficiency, is the increased friction due to vibration (both resonant and nonresonant) in the motor. By canceling out that vibration, the motor operated more smoothly, wore out more slowly, ran cooler, and used less fuel.

Of course, at the time, this only made economic sense with huge motors who's cost of maintenance, operation, and replacement justified spending megabucks in improving performance and endurance.

With the new technologies available to produce sound, or damp it in a given space... this technology could be used to improve efficiency and eliminate noise pollution from automotive engines, turbines, and a whole host of noisy machines including the fans in our computers.

I mean, if Bose can do it with your headphones, why shouldn't we do it with our environment...

Genda

- Why are there so few Zen performers? Because it's no fun making a curtain call to the sound of so many people clapping with one hand.

Negating Sound? Its like new cars....

[RobertTaylor]

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!!

Re:Negating Sound? Its like new cars....

[electrichamster]

"I have heard of something like that for cars ages ago, basically replays the engine sound over the car sound to negate it."

Alternatively instead of wasting all that money on a sound cancelling system you could just install hugeass speakers, sub and an enormous exhaust pipe, that way no-one will be able to even *hear* the engine noise over all that deafening dance music you'll be playing.
If you feel like it add undercar neons and go-faster stripes for extra style - they're guaranteed to bring the hot chicks from miles around.

now for the hard drives

[xobes]

The noisest part of all my computers i the hard drive, not the CPU fan.

Re:now for the hard drives

[Martin Blank]

Pick up some of the new fluid-drive-bearing units most companies are producing these days. I can hear my 60GB drives when they access, but the 250GB drive is completely without any detectable noise.

Of course, I do need one of the prof's nifty new toys for other parts of my system...

Re:now for the hard drives

[darkwiz]

The noisest part of all my computers i the hard drive, not the CPU fan.

How to reduce drive noise:
1. Take your hard drive off the mounts.
2. Find a 3.5" drive mounting kit and a piece of foam (styrofoam, or packing foam).
3. Mount drive on mounting kit, place on top of foam in the bottom of your case.
4. For completeness, ground the mounting kit to your case.

This will knock out a very large portion of your drive noise that is getting transmitted to the body of your case. It is a little Rube Goldberg, but it is very effective.

Re:now for the hard drives

[dfj225]

" The noisest part of all my computers i the hard drive, not the CPU fan."

I have one of the new design Alienware towers, and by far the most noise comes from the case fans. I have 2 seagate hard drives, and I can hear them somewhat, but the case fans are much louder. Although the fans themselves don't make that much noise, but the amount of air that they throw around does. If it is quite in the room, the whoosing sound can be quite loud.

Re:now for the hard drives

[Trejkaz]

The graphics fan is the noisiest component in my case. Those Gigacube Radeon 9600 XT Extremes are damn loud.

I also have a 30-35dBA fan which doesn't help with the noise. To help, I have an Sonata case, and when the case is on, the only thing I can hear is the clicks from the hard drive, and only when it's being used (during loading. Get more RAM if you are using swap!)

Normal operation is silent, or at least silent with respect to the other, louder computers that are not in Sonata cases. :-)

And of c

Re:now for the hard drives

[Kris_J]

Get a slower hard drive. 5400rpm drives are nearly silent, draw less power and are much cooler (thus you can turn down other fans). If you're concerned that this will affect your system's performance, you can compensate to some extent with lots of RAM.

Same tech as noise reducing headphones

[CormacJ]

I think this is how noise cancelling headphone do it - they just feed the external noise back into the earpieces after inverting it.

This would be a lot more useful...

[Trolling4Dollars]

...if it were applied to noise reduction of one's ass after a good bean based dinner. ;p

Huh.

[dupper]

When my CPU fan starts to make noise, I just whack my case until it stops.

Keep everything quiet

[nmoog]

Thats really cool. Its like those amazing bose noise cancelling headphones [bose.com].

I have wondered if it was possible to do this in my house. Where I live there is a lot of people who like to scream at each other alot, and it rather gets on the nerves. It would be cool if you could record your neighbourhood noises, and instantly replay them out of phase into your living room. Presto. The beautiful sounds of silence.

Re:Keep everything quiet

[electrichamster]

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*..........

Re:Keep everything quiet

[afidel]

Bose noise cancelling headphones suck, they aren't even the best active noise cancelling headphones available. Sennheiser has better models for around the same price. Far better than either though is the Etymotic ER-4P, these in ear canal headphone provide over 24dB of isolation, with some nice jazz playing you won't hear anything outside, headphone.com [headphone.com] has them for only $219, about the same as the Bose units.

Re:Keep everything quiet

[extra the woos]

Heh mentioning sennheiser in the same sentence as bose is like a sin, the two aren't even remotely comparable... bose is just like re-branded cheap paper speakers with a nice looking package etc heh...

Re:Keep everything quiet

[makapuf]

Note that it can be non realtime, too. If you record your neighbours when they make some noise, then, say, one hour later, play it back VERY loud, and you repeat each time they make noise, you'll see some noise cancellation effect quite soon.

Re:Keep everything quiet

[nmoog]

Dont get me wrong, I love earplugs - I live in a warehouse filled with dudes who love noise music. But Ive tried those bose headphones, and they are amazing. Earplugs DECREASE the noise, the headphones ERASE the noise. That makes a world of difference, especially on airplanes and the like (or offices with heaps of computers) where machine noise can drive you mad.

When you first put those headphones on it freaks you out a bit, because its like being in an anechoic chamber - the noises you use to judge dista

Re:Keep everything quiet

[wik]

I have both the MDR-NC20 and the older Bose model. If you get the Bose, make sure you pay the extra money for the newer model, otherwise you're better off with the NC20's. The older model has an annoying dongle that takes two AAA batteries. It also requires the batteries to be operating to play any sound. It also seems to amplify the bass a bit more than I like, but some people might thing that's a good thing.

The newer bose model has a battery up on one of the ear pieces (I believe a single AAA), no do

Mods...

[c0dedude]

Mod points to a poster who can point me to a download site for this or something like it, want to try it myself, will put a little speaker by the fan. Or is this not the way it works? Would a computer be too slow to pull something like this off sucessfully?

Re:Mods...

[cr0sh]

Something like this should be fairly easy to construct - whether it would work well or not, that is another thing.

First, get yourself a copy of Forrest M. Mims III's "Engineer's Mini-Notebook - Op Amp IC Circuits" (RS 276-5011) - probably not very easy to find (I believe it may be out of print - go to ratshack and ask). Alternatively, grab a copy of "The Forrest Mims Engineer's Notebook" (ISBN 1-878707-03-5).

Ok, now - if you have the mini-notebook, look on page 12 - if you have the other book, look on page

Alternatives to Noice Cancellation

[breakinbearx]

Although, it would be very very cool to get this technology to work on big loud things, and is very cost effective, for quite pc's, the Voodoo F:50 [voodoopc.com] does a very good job at keeping noise at a minimum, using no fans, only convective heat pipes, and using the entire case as a heatsink. Voodoo claims that their system operates at below 20 dBs, and cannot be measured in a room with regular ambient noise.

It never ends though

[irokitt]

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...

Re:It never ends though

[dlevitan]

No, that's not how it ends. I actually did this. I bought a very quiet hard drive (Seagate Barracuda IV), and a quiet power supply (Antec Trupower 330). But then the video card fan made too much noise, so I bought a replacement. But then the power supply was two loud, so out went the standard "loud" fan and in went a super-quiet pc power & cooling fan. Then the CPU fan and the case fans became too loud, so I replaced them all with the same fans as the power supply. But then the PS fan was still too loud, so I put in rubber spacers and undervolted the thing. But then the case fans were too loud and I undervolted them. But then the PS fan was too loud, and I undervolted it. Except that then my PS started overheating from the heat rising from my CPU. So I built a duct from the CPU directly to the outside of the case (which works fairly well). It's still too loud, and I don't really know what else to do except possibly undervolting the fan on my cpu. But if I start with that again, I'll probably never stop.

Re:It never ends though

[shadowbearer]

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

Re:It never ends though

[Patik]

I run Gentoo where it writes the files at the end of the compile/emerge.

You complied something in Gentoo and it finished!?

Re:It never ends though

[The Famous Brett Wat]

I have (and am posting this using) a VIA EPIA-M motherboard with passive heatsinking, no hard drive, an external fanless power supply, and no case fans. (It acts as an X terminal for another system.) There are no moving parts in the system at all. Believe it or not, however, I can hear a small electrically-generated squelching sound when there is ethernet activity (when all else is quiet in the dead of night). I could try WiFi, I suppose.

I could use this

[crass751]

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.

Absorbing technique instead

[fembots]

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).

Re:Absorbing technique instead

[reidbold]

Yeah man, damn plants and cubicles never shut the hell up.

Re:Absorbing technique instead

[utlemming]

I noticed that my University employs the use of masking. While taking a test in the religion department at my University [byui.edu], I noticed that the air conditioner was a little loud. Looking around, I noticed that there were four speakers placed near the doors of the religion professors. I figured this was to provide privacy for the professors when counseling people, and so passer-bys would not hear any of the comments. Anyhow, since then, I noticed that in the new building that was just completed, there are a lot

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[account_deleted]

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Wind tunnels...

[SmackCrackandPot]

We have a industrial PC that sits in a wind-tunnel. To us that's the largest cooling fan anyone would ever want.

Wrong direction

[Anonymous Coward]

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.

Re:Wrong direction

[reidbold]

Nah, I want faster. The money I spend on powering my computer is well spent, and would gladly spend more for more computing power.

If you want cooler and quieter, get a laptop I guess.

Wow, imagine...

[serutan]

A Beowulf cluster of those, attached to Rush Limbaugh.

Analog Devices app note for this four years ago

[dlleigh]

Analog Devices [analog.com] published an app note for this exact application four years ago.

"Adaptively Cancelling Server Fan Noise" can be found here [analog.com]. They were able to lower the whine by 30dB and the broadband noise by 20dB.

24 volt fans

[cyber_rigger]

If you don't need a massive airflow try a 24 volt fan. They still provide air circulation and are very quiet running on 12 volts.

Power Supply

[jmichaelg]

I installed an 80 mm Panaflow on top of a $30 all-copper heatsink to cut the noise from my computer but it didn't do much. As soon as the cpu fan noise was gone, the power supply noise was that much more noticeable. I ended up installing a new power supply. It was the best $80 I ever spent. The combination of a quiet cpu fan and quiet power supply result in a reasonably quiet computer. Not dead silent but at least it's no longer objectionable.

diy?

[frankmu]

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....

I must be retarded

[macemoneta]

I probably should have built a noise canceling tower or some similar nonsense, so I could get published.

Instead of all the research and electronics, I put a drop of oil on the axle and removed the dust from the blades with a q-tip. It's been silent ever since.

Silly me.

Or, instead

[lingqi]

Design quieter cooling technologies.

I mean it's not like it's not possible.

Case in point #1: NEC (in japan) has a water cooled computer now on sale to the teeming millions. water runs over the CPU and goes into a radiator to the back of the case. the radiator sits just outside of the power supply fan, which turns at an incredibly low speed (kinda like the apple G5 fans). Damn quiet.

Case in point #2: Mitsubishi, after not building any planes since WWII (zero fighter was by them, after all), entered the business-jet arena. The first thing they did was to design a new shape of turbine intake blades using computer simulation that cuts something like 10dB off the engine noise compared to traditioal strait blade intakes.

So, instead of brute forcing one's way around the noise problem, there are more elegant ways!

Whinny noise?

[6Yankee]

Sommerfeldt set about to find a way to drown out the whinny noise from built-in fans that cool computers and other electronic devices.

Did he try a fan with less horsepower?

I've got more sounds...

[lpangelrob2]

it only nixes the whine, not the whoosh

That's good and all, but what about my "braaagh"? I've also got a "whizzz!" and a "fhwhhhh" that still need to be dealt with...

Re:I've got more sounds...

[The Munger]

A "braaagh" eh? Sounds like you need to stop touching the blades as they spin around. And for the "fhwhhhh", I can recommend realigning the PC into a different magnetic field. Try turning it 30 degrees clockwise.

Or maybe just give it a good hard whack.

Not a good use of energy

[vandan]

Cancelling sound with sound sounds cool, but it's a waste of energy. Surely there are cheaper, more environmentally friendly ways of protecting our sensitive ears from the nasty CPU fan noise.

Every little bit counts. Just imagine if we didn't have to invade Iraq for their oil because we could properly manage our energy usage and R&D into renewable energy sources.

Re:Not a good use of energy

[Vellmont]

Whaa? Less than a watt of energy used to power speakers is a "waste of energy"? Your post is a waste of energy. Every little bit does NOT count. I'm really sick and tired of this nonsense of adding up miniscule "savings" and making them into big sounding numbers to the ignorant masses.

There's this attitude that's developed among the eco-freaks in this country that they can save the world by reducing their own personal consumption by .01%, because "every little bit counts. Not flushing your toilet to "

woosh would be hard to cancel

[nomel]

cause it varies depending on listenning angle, where the whine is pretty constant.

probably why he's having trouble.

I've used the headphones that do this...

[Phil John]

...as a pilot friend of mine has a pair (with mic boom as well). When you are flying a Cessna it's hard as hell to hear air traffic control, so these really help.

One really important use of these will be in ultra-quiet studio computers. Of course, its not to make sure the fan noise doesn't get recorded as its not a real recording studio if there isn't a separate recording booth/room (the studio I use in london from time to time is two rooms built within one large one, resting on a buttload of industrial springs, but I digress.

When you are listening to playback, making sure the singer was in tune, mixing the track, or whatever, you don't want ANY extraneous noise from fans. There is already a market for ultra ultra quiet pc's for this kind of application and advances like this can only help further the art.

Silent PC Review

[PoisonousPhat]

No Slashdot post about computer noise is complete without a link to Silent PC Review [silentpcreview.com].

SPCR

[Anonymous Coward]

Someone send this guy a link to
http://www.silentpcreview.com

Implementing noise cancellation for poor quality whining fans seems ridiculous in comparison to replacing the fans with better quality ones.

Quote from SPCR -
" What is a good inexpensive & quiet general purpose fan?

The 80mm Panaflo FBA08A12L with "HydroWave bearing" is widely used and recommended for its combination of low noise (21 dBA), good airflow (24 cfm), wide availability (but not in Canada where I type this) and low cost. At 7V, it is almost inaudible in most applications. At 5V, it is inaudible but still provides some airflow. We think of it as a workhorse, suitable for use as a case fan, CPU heatsink fan, or PSU fan replacement."

the best way to cancel pc noise...

[mgoodman]

...is to buy Zalman components ( http://www.zalman.co.kr/english/intro.htm [zalman.co.kr] )

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...

Not a new concept ...

[scdeimos]

... 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. ;)

Results will vary with frequency

[sammyo]

This is not a new idea and with a fairly constant tone may be possible but a complete solution for any frequency, direction, range and environmental configuration will be incredibly hard. Different frequencies will bounce and be absorbed by different materials, ah differently. ;-) So unless the damping tone is generated from the precise location as each 'annoying sound, a different calibration may be needed.

why bother ...

[cwg_at_opc]

when zalman have a fanless case:

• THGs review of the TNN500A [tomshardware.com]

THG sez you can still hear(barely) the HDD and optical, but if you're a noise weenie, do like the govt and replace everything with solid state(HDD and use CF for transportable media)
The case is stupid expensive at $1400US and the adventurous could probably build one for less by cannibalizing heat pipes from VGA coolers and stripping heatsinks from dead hifi amps, but there are ways of reducing PC noise without killing yourself or your bank account:

case - antec sonata or slk3700bqe

PSU - antec's yet-to-be-released phantom 350W PSU, or check this list:

• SPCRs list of PSUs [silentpcreview.com]

using vibration absorbing grommets for everything that vibrates(HDD, Optical, fans, etc.)

quieter fans:

• SPCRs fan list [silentpcreview.com]

OR, get longer cables and put the machine in an airconditioned closet; with a long USB2 cable and a powered hub, you might never hear your machine again. it'd just be you, your KB, monitor and a 7-in-1 media reader.

Noise Cancellation in Powermac G5

[amsr]

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.

Re:Noise and Heat

[thebes]

The amount of heat that a small microphone and speaker generate would be small enough that it would likely be transmitted through whatever the mounting system was made of, into the heatsink itself, and thereby take care of itselt. The heat increase would be negligible.

Re:No need to worry.

[hampton]

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.

Re:Why go through all this trouble?

[irokitt]

I have honestly seen computers put in freezers. Keeps it cool and eliminates noise at the same time. Leaves less room for the ice cream though.

Your solutions are crap

[Chuck Chunder]

Quiet fans tend to get noiser with age.

A box is not going to be good for heat dissipation or size constraints.

Water cooling is certainly not going to be cheaper or less complex.

If an active sound nullifier that will automatically adapt to the changing noisyness of a fan as it ages can be made for as little as $20 it is surely a more credible solution than your suggestions...

Re:Your solutions are crap

[Zakabog]

The fan will change noises as it gets older and somehow the microphone and speaker will remain perfect forever? If either the microphone or the speakers are damaged they'll end up creating more noise then they cancel out. What happens if the microphone starts picking up feed back then your computer's creating more noise than it started off with?

Re:Why go through all this trouble?

[kundor]

A quiet heatsink like this one [zalman.co.kr], perhaps?

While that would be fine, it actually costs more, and it weighs a TON (or at least a thousandth of one, which is nearly as bad.) If this noise cancellation can quiet a system just as much, for the same price, without the potential of ripping a hole in your motherboard, I'd call it a win.

Re:Like the noise cancelling headphones?

[Reverberant]

I thought the noise cancelling headphones worked because they were right against your ears.

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.

Re:Me too!

[gosh_d]

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 o

Re:hard drive whine

[BCW2]

Try Maxtor's fluid bearing drives. In an old AT box the only way I knew the drive was being acessed was the case fan slowing down. I now have 2 in my current box, along with Panaflo Low case fans (80mm and 92mm) and AMD's own heatsink and fan on a 2000+. Very quiet for the performance. Also check out the Volcano 10 heatsink and fan, thats quieter than AMD.