Pulsating PC...

[Random_guy]

In the last few weeks my computer has started, well, pulsing. Its mostly constant, at a regular rate of about one pulse a second, and very low frequency, so the entire case resonantes. I've tried stopping each case fan individually to see if that stops it but no joy, so its no individual fan.

I can only think of two causes:

1) as all 3 fans (front, back, and CPU fan) are 3 pin fans plugged directly into the motherboard, its possibly something the motherboard is doing, or
2) Its the PSU (being the only fan I can't stop) that is pulsing, and the case is resonating to it.

Has anyone ever come across something like this before?

[Steve]

It could be resonance from the fans, or it could be from your hard drives if you've got more than one?

I know my four Seagates go in and out of phase.

[TAKTAK]

Stop all of the fans (together) to totally rule them out, you can stop the PSU fan by pushing a bit of plastic carefully through the fan guard, and then turning it on.

Also, try disconnecting the optical drive to see if that makes a difference

[Pob255]

Try watching this.
http://tv.hexus.net/show/2008/11/Pac...e_s_the_noise/

[matty-hodgson]

I see you have the GTX275. Are you using the NVIDIA driver version 196.21? They had a problem with the GTX275 with overclocking and the fan randomly going from 40 to 50% every half second (Mine did it).

The 196.34 Beta driver is the exact same driver but it fixes this issue.

Hope this helps


Links:
Windows 7 32 Bit Driver - 196.32
Windows 7 64 Bit Driver - 196.32

[Singh400]

Mine does this, a swift kick fixes it.

[Time Bandit]

If you have an older PC it is quite possible that the bearing in one of your fans may be worn. As TAK TAK suggests you can try unplugging them one at a time to isolate the culprit (don't leave the CPU fan unplugged for too long!) Alternatively you can rest a finger gently on the edge of each fan, you are likely to feel a regular pusling if it is on its way out.

Resonance is also possible but can be harder to trace. If you suspect this then acoustic foam or silicone fan mounts can help.



http://www.acoustiproducts.com/en/antivibration.asp

Check the easiest things first!

[watercooled]

My first thought would be your hard drive(s). Try unplugging them then turn on your PC to see if it still makes the noise. Anything like this trial and error is the best way to find the cause - keep unplugging stuff until the noise stops.

[Random_guy]

Well, It had me flumoxed, and then I noticed that, after a while, it always went quiet. Then when my virus scan kicked in, it appeared again. So I stopped the scan, and it carried on for a while then went away.

That got me wondering. My virus scan always starts on my D:\ drive (an 80GB seagate with XP on it purely so that I can play very old games like MYST that I can't convince to install on W7).

So once it had quietened down I went into my computer, opened up my D:\ drive, and hey presto! the sound reappeared.

So now the only question is, what, if anything, can I do about it?!

[matty-hodgson]

So now the only question is, what, if anything, can I do about it?!

Tiny little strip of rubber between the HD and the case would help.
Or suspend the HDD on rubber bands would eliminate most noise completely.

[Singh400]

Well, It had me flumoxed, and then I noticed that, after a while, it always went quiet. Then when my virus scan kicked in, it appeared again. So I stopped the scan, and it carried on for a while then went away.

That got me wondering. My virus scan always starts on my D:\ drive (an 80GB seagate with XP on it purely so that I can play very old games like MYST that I can't convince to install on W7).

So once it had quietened down I went into my computer, opened up my D:\ drive, and hey presto! the sound reappeared.

So now the only question is, what, if anything, can I do about it?!

Gonna sound stupid, but the simplest things work. When my HDDs are "whining" I just slightly elevate the PC, and the sound stops. You could get a silencer kit, or I've heard rubber bands work wonders.

[Rob_B]

I suspended mine between 4 elastic strips, takes up a lot of room (as it hangs free) but there is no vibration whatsoever. If you can't imagine what I mean I'll try to explain better!

EDIT: Just been reading Hicks12 post & this pic is exactly what I'm on about. wrap the elastic figure of 8 around the front & back et voila!

[abaxas]

If you have >1 hard disks, the disks all spin at different rates.

Eg 7200 rpm, 7200.1 rpm.
This will casue a slow in and out effect like the pulse you describe. All due to the disks being in sync then out of sync. Ie somtimes they cancel each other out, other times amplify each other.

Only way to fix that is to use rubber mounts.

[Random_guy]

Thanks to all that have responded. Looks like I'm going to be spending my weekend playing with rubber bands! I'm glad I found the source though. I'm happy with my PCs performance at the moment, and really didn't want to have to replace anything, so I'm glad its nothing more serious. Thanks again

[Phage]

Glad it's not a euphemism then. All those rubber bands...