Mysterious electric hum...

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Illu
Posts: 4
Joined: Tue Mar 05, 2013 3:12 pm

Mysterious electric hum...

Post by Illu » Tue Mar 05, 2013 4:02 pm

Hey guys! Long-time reader, first time poster. I hope this is the correct place to post this, as I'm not sure which component(s) might be at fault. Firstly, here's my system:

Case: Fractal Design Define R3 (atx)
Fans: 5 Nexus Real Silent 120mm variable speed (via speedfan, just slightly audible from about a foot away)
Motherboard: ASRock Z77m
RAM: 8GB G.Skill
CPU: Core i3
CPU Cooler: Cooler Master Gemini 2 (replaced stock fan with a Nexus Real Silent, as above)
GPU: Asus GTX 660
SSD: 3 SSDs (Intel X25m, Crucial m4, and a Samsung 840)
Hard Drives: N/A
PSU: Corsair AX750 Gold / Seasonic SS660 Platinum

And here's my problem: I'm hearing what sounds like a loud fan or electric hum, audible from about ten feet away and rather annoying. It isn't present right after booting, but I notice it after my system has been on for at least 20 minutes or so (both idle and while gaming). It's still very audible after disabling all fans (including the two GPU fans, which are almost silent anyway). To diagnose further, I removed the GPU from my case (using the i3's onboard graphics instead) and could still hear it. When listening inside the case, it seems to be coming from the PSU or motherboard area, it's hard to pinpoint. I thought it was probably my Seasonic, so I replaced it with an old Corsair I had, and did not notice any discernible change. I also tried disabling C1E in the BIOS which also didn't help. I've attached a recording using a cheap microphone: for some reason I had a hard time capturing the sound (probably just low quality hardware): it's a very rough approximation of what I'm hearing (except much louder and with a higher pitch). The clicking sounds are the fans trying to spin up (I used some pens to block them temporarily).

Having spent a lot of time and energy trying to get a low-noise system, this has been frustrating and I'm out of things to try. And so I turn to the experts :). Any ideas?

frenchie
Friend of SPCR
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Joined: Tue Jul 08, 2008 4:53 am
Location: CT

Re: Mysterious electric hum...

Post by frenchie » Wed Mar 06, 2013 7:45 am

Hi,

Welcome to SPCR !

Have you tried the tube method ? Take a tube (the cardboard inside of a roll of paper towel works great), put your ear at one end and move the other end around the open case. It should help you pin point where the noise is coming from.
It is strange you still hear something when no fans are running, and you don't have a traditional HDD...

As for moving parts, the only thing left is the PSU fan...

If it's not that, it's electrical noise. Is your cpu overclocked at all ?

xan_user
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Location: Northern California.

Re: Mysterious electric hum...

Post by xan_user » Wed Mar 06, 2013 7:53 am

how is the house wiring?
can you try PC on a different mains supply? -like at work or a friends house?
do you use a UPS? - if so try unplugging it form the wall and running it from the battery to see if noise continues.

Illu
Posts: 4
Joined: Tue Mar 05, 2013 3:12 pm

Re: Mysterious electric hum...

Post by Illu » Wed Mar 06, 2013 11:13 am

frenchie: The PSU fan wasn't spinning, it only spins under higher load. I tried the cardboard tube trick, and it seems like the sound is coming from both the PSU and the GPU/motherboard (I couldn't tell which one). The PSU seems to be making a quieter, higher pitched sound, and the electric drone is coming from the GPU/MB area. The overall sound from outside the case is therefore a combination of these sounds. I also don't overclock at all.

xan_user: I'll see if I can try at a friend's house sometime. I'm in a fairly old house, but the wiring was redone about 2 years ago. I just use a surge protector/power strip, I tried plugging in the PC directly to the wall, but noticed no change.

frenchie
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Location: CT

Re: Mysterious electric hum...

Post by frenchie » Thu Mar 07, 2013 7:57 am

Since it's not the gpu, or the psu, or the hard drive, the only thing left in the case is the motherboard... :roll:
You could try an rma if it is still under warranty, and see what happens with the replacement.

Illu
Posts: 4
Joined: Tue Mar 05, 2013 3:12 pm

Re: Mysterious electric hum...

Post by Illu » Thu Mar 07, 2013 9:14 am

What part of the MB could make so much noise, though?

frenchie
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Location: CT

Re: Mysterious electric hum...

Post by frenchie » Thu Mar 07, 2013 9:26 am

Coils usually, probably in the power circuitry somewhere... (those black cubes around your cpu socket)

Illu
Posts: 4
Joined: Tue Mar 05, 2013 3:12 pm

Re: Mysterious electric hum...

Post by Illu » Thu Mar 07, 2013 10:34 am

Is it just luck of the draw, or are some MB manufacturers better than others?

frenchie
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Posts: 1346
Joined: Tue Jul 08, 2008 4:53 am
Location: CT

Re: Mysterious electric hum...

Post by frenchie » Thu Mar 07, 2013 10:56 am

It tends to be a certain combination of motherboard and/or gpu and/or psu that causes the noise. It's hard to figure out exactly what is causing it. In your case, the motherboard is the only other possibility I can think about since the noise is still there with all the other stuff removed.
On one of my machines, I can get rid of the coil noise by changing the frequencies on my gpu (slight gpu core overclock and slight gpu memory underclock)...
Try a slight overclock (faster clock speed = high frequency, and that should give you a higher noise pitch which you might not be able to hear).
If that doesn't work, try rma, you might get lucky.

As for the manufacturer, I don't know. The technology is what matters IMO, more than the manufacturer...
My machine that used to have a slight whine is Asus motherboard, Seasonic psu and gigabyte gpu.

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