help with pulsating noise

flextone · Post by **flextone** » Wed Oct 25, 2006 5:50 am

Hi guys

i`ve had my new pc for a week now, and yesterday i started hearing a noise i didn`t hear on the first few days, which sounds the minute i turn the pc on. it`s a kind of low hum pulsating in a cycle, 5 seconds hum, then 3 seconds silent, something like that. i can even feel the case vibrating with the hum cycle. the strongest vibrations come from the top end of the case. i don`t think it`s the fans spinning at different speeds and thus making a pulse cause i can hear and feel the same pulsation even when i change the speed on the zalman.

my case is an antec sonata 2. cpu fan zalman 7700. no vga fan or front fans, only the zalman, the rear 120mm and the psu, which all seem fine when i take a look inside.

any ideas?

Post by **NeilBlanchard** » Wed Oct 25, 2006 6:20 am

Hello,

Are there two HD's in the system? It sounds like it's a very slow "beat" frquency, and if there are two things that run at almost the same speed, it could produce this.

flextone · Post by **flextone** » Wed Oct 25, 2006 6:37 am

but this happens even when the machine is idle and i`m sitting watching tv, it doesn`t come on or off, just constantly

nici · Post by **nici** » Wed Oct 25, 2006 6:45 am

HDs vibrate, and can cause this. If you have your HDs hardmounted, this is likely to be the cause. Decoupling the HDD(s) or adding some heavy damping should solve the problem if it is the HDDs. Or as Neil said, it could be airborne as well, in wich case it would be harder to silence. You can start your system wihtout the HDDs connected to check if they are causing it, if you have several try with some on and some off. Fans can also cause this, but that should not be as noticeable and i would be surprised if that was it.

dfrost · Post by **dfrost** » Wed Oct 25, 2006 7:38 am

nici wrote:HDs vibrate, and can cause this. If you have your HDs hardmounted, this is likely to be the cause. Decoupling the HDD(s) or adding some heavy damping should solve the problem if it is the HDDs.

Here's an effective and cheap methodto isolate HDDs in Sonata drive sleds.

flextone · Post by **flextone** » Wed Oct 25, 2006 8:30 am

ok, ill check and see if it`s the HD`s and tell u how it goes

flextone · Post by **flextone** » Wed Oct 25, 2006 10:20 am

ok, you were right, it`s one of the drives. a 250gb WD that sits below another WD.

i`m sure that sound wasn`t there the first couple of days, what could have happend?

isn`t the sonata2 supposed two eliminate that kind of noise with it`s rubber thingies where the screws go?

btw, i have only two screws on each hd, though it feels solid

jackylman · Post by **jackylman** » Wed Oct 25, 2006 11:47 am

flextone wrote: isn`t the sonata2 supposed two eliminate that kind of noise with it`s rubber thingies where the screws go?

In my experience, rubber grommets are no match for hard disks that kick like mules (i.e. most modern ones).

flextone · Post by **flextone** » Wed Oct 25, 2006 1:43 pm

so the only option is damping?

nici · Post by **nici** » Wed Oct 25, 2006 1:49 pm

Just using some foam or sorbothane to mount the HDs in the sleds might work, like in the thread linked above.

I did notice a funny(not really) thing with a 80Gb WD once, if i put in a P180 sled the noise would at least double. There was a Seagate HD reviewed on SPCR at some point wich also got noticeably louder when placed near a solid surface. Both of these were high-pitch noises though if i remember correctly.. not low frequency humming.

You could also try and move the HDDs farther from eacother, like putting them in the top and bottom slots.

Also does this happen with the case open? Just curious...

Felger Carbon · Post by **Felger Carbon** » Wed Oct 25, 2006 2:02 pm

flextone wrote:ok, you were right, it`s one of the drives. a 250gb WD that sits below another WD.

Actually, it's not one of the two drives, it's the two drives together, coupling thru the metal chassis. Remove either drive and the problem will go away.

So, the problem is not to dampen/isolate both drives - isolating one will do. I suggest you peruse the "show us your suspended HDD" sticky in the General Gallery forum and see if any of the various methods tickles your fancy.

flextone · Post by **flextone** » Wed Oct 25, 2006 2:41 pm

ok, i`ll do that

p.s

again, do you think this could be something that started yesterday? cause i`m almost sure that the noise wasn`t there the first few days

pyogenes · Post by **pyogenes** » Wed Oct 25, 2006 3:33 pm

flextone wrote: again, do you think this could be something that started yesterday? cause i`m almost sure that the noise wasn`t there the first few days

It's possible that after the drives were "broken in" they settled on normal operating rotations that lends itself to making the pulsing sounds.