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noise canceling for pcs

B

bladeiai

[H]ard|Gawd
Joined
Dec 26, 2004
Messages
1,126
I read awhile back that someone was working on making a thing with a speaker you put into you pc that used noise canceling to eliminate the sound of fans and components. has anyone heard of this and if anything was ever released?
 
You can't just...STOP noise. Y'know, physics and all. But, you could, with a lot of work, create something that made a constant white, static noise, I believe. Doesn't seem worth it, though.
 
actually according to the article I read you can, you just have to create a perfect opposing wave length
 
bladeiai said:
I read awhile back that someone was working on making a thing with a speaker you put into you pc that used noise canceling to eliminate the sound of fans and components. has anyone heard of this and if anything was ever released?
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That would be a great idea if some company implemented it... :)
 
What's the point of canceling noise with more noise? Build a quiet computer or turn on a fan or air conditioner so that it actually does something (cools computer) while it create white noise.
 
the point is you can have a computer that has several fans running and cooling more effectivly and be silent- not quiet but completely inaudible to the human ear
 
thank you = )

I read somewhere awhile back that they were trying to apply this to PCs at some univsity or grad school somewhere
 
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Not only that but it looks like a giant red penis. I hope he doesnt have a side window :p
 
Mr. K6 said:
lmfao, it's just ludicrous to replace sound with a different sound. That's like saying it's too bright outside so you put a flash bulb up to your eyes and take a picture :p
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I'm guessing you don't know anything about waves.

They use phase-inverting sound generation in noise cancelling headphones. I would imagine that it would be much harder to generate a perfect inverted phase anywhere away from right over your ears though. Due to the speed of sound, some noise-generating elements in a PC case will be farther away from your ears than others, so the phase for your ears will be different than for a phase inverter placed inside the case. It would be difficult to cancel the noise because of this, and it could make things a lot louder depending on the placement.

I really haven't seen any successful demonstrations of sound cancelling other than with those expensive headphones.
 
Zinn said:
I'm guessing you don't know anything about waves.

They use phase-inverting sound generation in noise cancelling headphones. I would imagine that it would be much harder to generate a perfect inverted phase anywhere away from right over your ears though. Due to the speed of sound, some noise-generating elements in a PC case will be farther away from your ears than others, so the phase for your ears will be different than for a phase inverter placed inside the case. It would be difficult to cancel the noise because of this, and it could make things a lot louder depending on the placement.

I really haven't seen any successful demonstrations of sound cancelling other than with those expensive headphones.
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Yeah, though it only works in theory.

In practise there are just too many hurdles to cross:

1. Room acoustics. Sound phase can alter slightly as it bounces off walls etc. so some sound will be cancelled, other frequencies may be amplified.

2. Hardware/software not quick enough. I don't think it's possible in a pc to have the microphone record a sound and then have a perfect opposite wave played at EXACTLY the same time in order to cancel out the sound wave. There's an inherent delay and that's enough to make it all utterly ineffective.

3. Recording the sound in the first place is tough enough. Again, you have problems with accoustics and you'd need a bloody good microphone to truly capture the sound.


There are probably many other reasons, but those are the main ones.
 
When noise cancelling technology was first announced and implemented a few years ago as a luxury feature to quiet the ride in Cadillacs a bunch of us were excited by the possibilities. We posted here about the possibility of doing it inside a computer case. At the time it was too new, too big and too expensive for twinked computers but the designers have clearly shrunk the equipment (if it's being used in headphones.... and I'm pretty sure Bose has been selling some for over a year).

So, yeah, it can be done. It is being done. Not sure who's doing it with personal computers yet. A competent electrical geek could do it - I imagine - with a microphone, a tailor made chip (that calculates the inverse of a sound wave) and a speaker. Frankly, a standard sound card running the right software could probably do it...

Hmmm.

Alright, such a chip must exist and be running at low voltages already in those headphones.
 
spine said:
Yeah, though it only works in theory.

In practise there are just too many hurdles to cross:

1. Room acoustics. Sound phase can alter slightly as it bounces off walls etc. so some sound will be cancelled, other frequencies may be amplified.

2. Hardware/software not quick enough. I don't think it's possible in a pc to have the microphone record a sound and then have a perfect opposite wave played at EXACTLY the same time in order to cancel out the sound wave. There's an inherent delay and that's enough to make it all utterly ineffective.

3. Recording the sound in the first place is tough enough. Again, you have problems with accoustics and you'd need a bloody good microphone to truly capture the sound.


There are probably many other reasons, but those are the main ones.
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i think for sound coming from something as reptitive as a fan in stationary space/position (computer case), it would be relatively easy to design a noise canceling module. you would just plug in differing amplitude/period/phase components into a wave generator until the sound is reduced. maybe standard wave parameters can be obtained from manufacters or hobbyists/researchers with measuring devices as a starting point

am i making it sound easier than it really is?
 
Yeah I think I've seen some headphones that claim to have sound cancelling capabilities. Zalman unless I'm mistaken.


I've no idea how effective they are. But with headphones, you have no problems with room accoustics so I'd imagine they could make them pretty good.
 
Mr. K6 said:
lmfao, it's just ludicrous to replace sound with a different sound. That's like saying it's too bright outside so you put a flash bulb up to your eyes and take a picture :p
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You actually can experiment with this at home (the audio cancellation technique).

Take two of your home speakers. Wire one correctly, wire the other one back wards. Play the exact same sound out of both (not a stereo image, but a monaural source). Now change the wiring back on the other speaker, replay the same exact sound "Without" changing the volume. Walaa, notice that while not completely canceled, you'll notice that the volume levels are quite different as the out of phase speaker essentially is cancelling out the waveform from the other speaker. The article linked was much more detailed and goes into the details more in depth, but you are not "replacing " one sound with another but basically "crashing them together" to cancel them out. Interestingly, this is why instructions for installing multiple Subwoofers in automobiles specifically warn about not wiring out of phase as the efficiency would be greatly deminished due to this cancelation effect.
 
This theory wouldn't work in a case... Mainly because of distance of the sound waves and such in the case, the fact that the waves would bounce off of the side of the case and such.

Noise cancellation in the headphones though, it does work. I tried those Bose headphones (like $400), and my mom and the guy were having a rather loud conversation about the price and such, and I never heard a single sound from them, I felt a little bit of vibration though.
 
Anybody ever seen the foam cube setups that are like a checkerboard-lets say reds are prominent while blacks fall in depth right behind the reds? Those are supposed to work by catching all the waves in pockets and absorb them, I was in a room with that setup in Paris and it worked.
 
I don't think accoustic foam would fit in a case... or be very good for airflow :p

bah, plus that damn stuff costs like 60 bucks per square foot because the manufacturers are a bunch of freaking pirates.
 
Acoustic foam, dynamat, and Brownbread... Those are vibration dampeners as well as sound dampeners. And yes, they are F'ing pricey. A small roll of dynamat is $70.
 
Damn, somebody beat me to it:
spine said:
Yeah, though it only works in theory.

In practise there are just too many hurdles to cross:

1. Room acoustics. Sound phase can alter slightly as it bounces off walls etc. so some sound will be cancelled, other frequencies may be amplified.

2. Hardware/software not quick enough. I don't think it's possible in a pc to have the microphone record a sound and then have a perfect opposite wave played at EXACTLY the same time in order to cancel out the sound wave. There's an inherent delay and that's enough to make it all utterly ineffective.

3. Recording the sound in the first place is tough enough. Again, you have problems with accoustics and you'd need a bloody good microphone to truly capture the sound.


There are probably many other reasons, but those are the main ones.
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Re-reading my post, it sounds a bit ignorant, sorry, here's the clarification:

As stated above, it's close to impossible to do it with today's tech in an open situation (i.e., a room). Even if one could get the the PC to produce sound within a certain range (which would be hard based upon the fans spinning at different RPM's depending on load, memory access, HDD access/spin, etc. etc.), getting the correct acoustic negative to cancel it would still be close to impossible. As stated by spine, you could cancel the fan noise, but then the HDD seek would break your ear drums :p. I thought the original intent here was to use white noise to cover over the sound of the computer, which would be a waste, more or less, as I previously stated. However, developing something for noise cancellation would be insane, although incredibly cool. Maybe it could be an upgrade for BOSE's new speakers that adjust themselves based on the acoustics of the room (forget what they're called). But if BOSE released in a few years, it would probably be $20000 + the program, those speakers are already $16000 :eek:
 
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