Redusing The computers' Noise

[DrCIH]

Hi everyone! I am a student in Technical Univercity in Plovdiv - Bulgaria and I need your help for something.

For many many days, I've been asking myself how to reduse this disgusting noise form my computer without making him a hothouse. As we know each sound isolation material is also termo isolation (forgive my englis)
So, is there another way to reduse the sound? Probably yes.
I asked myself how do they do it on airplanes. Well, we know that the sound has a diagram. If we have a circuit, which has a microphone that sences the noise and makes its diagram upside down, the graphic of the noise will be a stright, which means that that there will be no sound. So I need a circuit which has a microphone and a speaker thad makes the the upside down sound. This is the best way to reduse the computer case's noise. Can someone give me that ciscuit???

 

[mvs sarma]

Hi DrCHI
basically you may have to locate source of noice say from 1. HDD, 2. PSU cooling fan, 3. CPU cooling fan, 4. General fan additionally provided in the cpu cabinet, 5. Floppy and CD drives.

Once this is possible you can very well replace a 12v Fan or the device causing noice.
this exercise, perhaps has to be done or one has to pay for a service technician.
this could solve your problem i beleive.

sarma

 

[DrCIH]

I want to place this thing on the case. On a closed case, so that with one device to solve the whole problem. And the idea is to test another way for noise reduction. I think this is the best way and if made good it reduse all the noise, so that the case can be completely scilent.

 

[Someone Electro]

Water Cooling.Replace all fans whith watercooling heatsinks. You could probobly mount the CD drive on ruber vibration insulators.And only solutiong for the HDD is to buy a silent model.

 

[DrCIH]

I know! I've done it before. I know all about silent HDDs and fans or water cooling. The point is to make this circuit. Imagine a way to reduce every case's noise, not only computer's. And I want to do exactly this thing. Just for the experiment.

 

[Nigel Goodwin]

You mean you want to try and cancel it out with a phase reversed sound?.

This is only possible over a specific small area, outside that area the noise is louder, as you now have two of them!.

 

[Someone Electro]

Also here is a problem cause the noise soruces are scaterd around.

If this was practicly posible you would prbobly see comercial case moods that do this

 

[jpanhalt]

Some people have used noise-cancelling headphones to attain the effect referred to by Nigel. "Bose" makes a commercial unit that is advertised in Scientific American and elsewhere. I have also found self-made units on the internet. Unfortunately, I can't find the links right now. Try Google. The headsets do work, in part. But, you have to get used to wearing them. Since hearing is adaptive, that is, the more quiet the room, the more sensitive your hearing becomes, some people have had success by adding other, less annoying sounds. The Bose headsets include a background noise, which is probably for that reason. The lowest frequencies, such as the sympathetic beating of two fans, are hardest to get rid. A lead-lined room is probably the only solution to that There is a lot of published literature on the adverse effects of low frequency noise that you may want to look at. John

 

[jpanhalt]

Here are a few references:

1) http://www.defra.gov.uk (look for Leventhall on the effects of low frequency noise)
2)J. Applied Psychology 2000; 85:779-783
3) **broken link removed**

 

[Someone Electro]

If you ask me a better solution is just to play music in the background to cover the sound up

 

[justDIY]

just slow the computer down, or if you have an AMD powered computer, make sure cool and quiet is enabled - this will slow the system down for you automatically. less speed = less heat = less noise

the system I built myself in July has 5 fans in it, but is very silent most of the time. The key is the AMD Athlon X2 processor reduces its speed and voltage when it's not working very hard, which allows the temperatures to go down. In turn, the motherboard senses this, and reduces the speed of the fans. When I'm playing a very intensive game there is some fan noise, but not much... the only big noise comes when the ambient temperature is very high, which won't be a problem for the next ~6 months in Michigan.

 

[evandude]

To go along with what nigel said, here's an analogy. Picture dropping a pebble in a pond, and it sends waves outward in all directions. Now you can imagine that if you drop another pebble somewhere else in the right way, you can cancel the waves in a particular target spot. However, look at the rest of the pond; now there's two sets of waves everywhere, so the "noise" is twice as bad. The reason noise-cancelling headphones work so well is they're very close to your ear, and they're in a shell and insulated enough that they don't produce very much noise to the outside world. They're focused on your ears, and nothing else.

Now picture throwing a big handful of pebbles all over the place, you end up with a big noisy mess. The most important point here is that there is NO POSSIBLE WAY for you to cancel all that noise by throwing a single pebble in a single spot. Just like there is NO WAY to cancel all the noise of a computer by placing a single speaker inside it.

Now notice that the only way you can cancel the waves of one pebble in all directions is to drop another one in exactly the same spot at the right time. In terms of sound, this is even worse, as you're in 3 dimensions now; You would have to have a speaker right on top of every noise source. But, of course, you can't place a speaker INSIDE a hard drive or processor fan or anything like that. So you would have to place it as close as possible. How close is "close enough"? Well at low frequencies (hundreds of Hz), sound wavelengths are on the order of feet, but at 1Khz the wavelength is just over a foot, so placing a speaker an inch or two away is a pretty significant error. So really, you will have to limit yourself to low frequency cancellation. Plus you've got the issue of your noise not being a point source. And, you have to consider how large of a speaker/woofer you would have to use to deal with a particular noise: a tiny speaker is NOT going to produce very low-frequency sound. And you also have to consider the directionality of the speaker, vs. the more omnidirectional nature of many noise sources.

My guess is that by the end of your experimentation, you'll end up with a case full of little speakers that sounds like a screwed up jet engine. Based on your questions, you must not know much about this... but all you need to do to get an "upside down" wave as you ask, is use an inverting amplifier... or even a non-inverting amplifier, and just flip the speaker terminals. That probably sounds way too simple to work, (and there's a good reason for that) but it's exactly what you're asking for.

Once again... there is a REASON you don't see this implemented in computers already. If noise cancellation was as simple as a single microphone, speaker, and a small amplifier circuit, then don't you think EVERY noisy piece of equipment would come with one preinstalled?

 

[audioguru]

The speaker that makes the "upside-down" cancelling sound will also be heard by the microphone that picks up the noise. At half-wave distances of frequencies between them then there is positive feedback to produce a howling feedback sound.

Use larger fans that spin at quiet slow speeds.