Finding source of noise in computer
 

Hello,
I would like to ask you this interesting question. I am trying to decrease volume of noise coming from computer as much possible, till one point from where I don't know exactly what's the source of noise.

"That noise" starts coming out of computer few seconds about booting, not while POST test, and then it's constant. To me it seems like it's coming out of cpu, but not fan. (I have disconnected all hard drives, have gpu with passive cooling installed, and it's still there. Cpu is AM3 socket AMD Phenom II 810 processor, and motherboard is Asus M4A78T-E.

Also, my other computers with Intel and other AMD processors does not produce such a noise.

Does that noise come out of CPU? is it some "computing sign" of processor (assuming that during first seconds of booting are perfectly quiet), or kind of general problem of AMD (or AM3 socket) cpus.

Thanks for help, and sorry I made it this long...

Fans are a first suspect. You can stop the CPU fan for a few seconds by holding it, same for the power supply fan but use non-conducting stick, dangeous voltages inside

If that is not the source, suspect any switching power supply, both in the main power supply and the on-board supplies. Both magnetic cores and capacitors can produce sound, magnetic cores being more likely. On the main board, pressing onto such a component would change the sound and perhaps you can feel the buzzing. For the power supply, if this is suspect, replace it, way too dangerous to touch inside.

jlinkels

Thanks for your reply Jlinkels,
I'll try it, and then post back results.

One additional bit- Stick the non-conducting stick in first to stop the fan from getting started, then turn on power. Sticking the stick in
after power is on sometimes leads to fan bits all over. I wonder how I know...

Noise comes from bearings on fans(try oil!), or blunt fan blade edges. It can be exacerbated by putting them in a tin box like a pc case.

Thanks for your replies,
so I tried stopping fans for a second, but it's not them obviously. The noise seems to be coming outside the cpu itself, or some motherboard component.

miyatake: thanks for advice, my grandpa actually did same thing. It has been a long time we have nice souvenir in cupboard.
business_kid: I have that computer in pc case about 3 days, but it's still same. I could try oil but I don't even know how/where to correctly apply it. (Guess I'll take a look at Google).

You said it is not the fans, so there is no point putting oil in them.

Can you record the sound and put the MP3 somewhere?

jlinkels

It's tricky.
Noise is coming from vibration. Electronic parts don't vibrate as a rule. No.#1 source is the fan inside the power supply.
When you look at the centre boss of the fan, on one end there will be a gap trickle a few drops of oil in there as you turn it.

Hi,

What about localizing the noise? If it is mechanical noise it can be transferred and difficult to locate. You could try a long piece of wood dowel or even a 12" plastic ruler to pin point the noise. Place the rod/ruler at a point on the MB then the opposite end of the ruler to your cheek or ear. Move the ruler point to point to localize. You can buy a special stethoscope for electronics work but this rod/ruler will work.

If the problem is the PSU, swap out to see if things change. To get inside the PSU and not experienced then bodily harm is possible. The modern PSU do have small signal transformers with laminates that could be loose that would transfer mechanical noise through the mounts and case. I would think that a user could localize a noise of this sort.

Be sure your MB mount screws and standoffs are tight & secure to the chassis.

You said that the HDD were disconnected. From power? If not the source could be the drives. Don't forget the optical drives.

What pitch or frequency of the noise? Low or high?

You could do a touch on the local MB supply caps, one handed(one hand behind back) use the other to approach slightly by placing a finger over each without actual touch. You will feel the vibration the closer your finger gets to the source. You will feel some heat, if excessive then that could be the source.

If it's a resonance problem then the source could be localized with proper test equipment.

If it is a switching problem then swapping/replacing will be the best choice. Especially if you do not have service experience.

Your big problem is identifying the source.
:hattip:

The folks over at SilentPCReview might be able to help you with this:

http://www.silentpcreview.com/forums/

Neil

Thanks for replies,
I am sorry for replying after longer time, I didn't see this thread. It was not displayed in My LQ - New Subscribed Threads. Could it possibly be a bug? so far, each time someone replied to threads I have participated in, thread was displayed there.

Back to topic. So I rebooted computer on&off few times, and I came to this results:

You asked me about pitch of noise. Well, it has lower pitch (hope it makes sense) if it can be said. First "charging" sound can be heard (like when you charge taser, or from pc games some big electric gun), then it is followed by the noise I am talking about. I am still not sure if it's not standard noise for these computers, but as I said before, other ones don't produce nothing like that.

I'll disconnect all drives both from power and Sata cable, just to make sure. Then I'll post back with results.

Also, I think it's not kind of noise made by not properly installed component (or damaged). It all looks like it comes out of component's inside, I'd say cpu could be the right one to blame.

neilgunton: Thanks, I could use that one.

Ok, so I looked through it all again.
1. Disconnected all drives
2. Disconnected all fans which weren't needed.
3. Held main CPU fan for a second.

Noise continued coming out, so now I am about to look on PSU. It will take me some time though, so please don't expect me to reply immediately.

Alright,
PSU is not source of noise too. (I put it outside case, and noise kept coming from inside).

Now it seems it has to be CPU or motherboard itself. It looks like it's coming directly from CPU, but I am not sure how to verify it. One option is to start computer without CPU, but noise seems to produced just after POST test, so this way should not work. Also, my CPU is AMD Phenom II 810 - but for example, there is no such a noise within AMD Phenom II 970. (I can't afford to turn that pc down, so I can swap processors or heatsinks/fans).

Hi,

How did you localize the noise for the CPU or HSF?
Power down the system, remove plug then remove HSF from the CPU.

Plug the HSF into aux fan plug on another system or use a separate PSU loaded. If the vibrations are with the HSF then replace it.

What condition is the paste on the CPU, sticky or dried out? Clean & Put new paste compound on processor and make sure the replacement HSF is clean. While HSF is removed, do you see any dis-colorization on the MB or capacitors? Sometimes the MB regulators have a small heat sink, check for tightness/security.

What about the Stethoscope technique to find the noise source? Finger technique results?
Your not providing feedback for suggested techniques is not helping us to help you.
:hattip:

Hello,
I localized it using my own ear. I moved PSU out of box, and then moved head near to the motherboard. HFS should not be the one, since fan spins while computer's running POST test, and there is no such a noise. I may try it anyway, however I am not sure where to insert it, since my fan connector consists of more than three pins.

Paste on CPU is really dry (I'd say there is almost no paste left at all), but Phenom II 970 running computer didn't have paste installed too, and was absolutely quiet.

Motherboard should have only passive heatsinks, I will search it again just to be sure.

About Stethoscope, I don't have any stethoscope-like object to use for this purpose, I could buy it, but I think I localized the main area of noise's source. Also, finger technique, I tried it, no results. Just to get me right - the noise is not like some special, not ordinary noise - it looks just like "computing noise", but much louder than standard of today's cpus (at least those which I have heard running).

Thanks for help, and sorry I didn't write you about Stethoscope and finger techniques results.

EDIT: Also, turned off most of "special features" my motherboard has, but still no good results.
EDIT2: Eh, just to try to make your vision about the noise better, Intel Pentium 4 CPU is more silent.