I have a PC that produces audible noise/screeching correlated to network activity. The noise is high-pitched and somewhat difficult to locate, however it seems to be coming from the power supply. It's clearly audible over the PSU and CPU fan noise. Has anyone experienced this before? Does anyone know the cause and/or solution to it?

  • Ethernet cable unplugged: white noise
  • Ethernet cable plugged in: noise with HF components
  • Ethernet activity: noise with varying HF components

More info: It's a very cheap 350W ATX PSU that has run continuously for 2 years. It's also going to get replaced tonight by something a little better.


The cause cannot be diagnosed remotely. But according to your information, this might be a noise coming from the inductor. With the time the bondings between the laminated strips in a inductor core may be weaken leading to generate a high frequency noise.

  • Due to the cheapness of the PSU, I'm getting you're probably right. – geofftnz May 25 '09 at 3:48
  • You can open the cover of the PSU and check for the exact component that makes the noise. If it is a transformer you may fix the matter just using some glue. BEWARE OF THE CHARGED CAPACITORS!! The 2 Big capacitors can hold a massive amount of charge. – Chathuranga Chandrasekara May 25 '09 at 6:04
  • I opened it up (again, already replaced a noisy fan). The grommet/cable clamp fell apart, all the components look very cheap and under-specced, so the PC now has a new better quality PSU. – geofftnz May 25 '09 at 21:12

I have heard of something similar. I would guess that the power supply either is going bad, or the motherboard could be going, as well. Either could cause the power supply to make weird noises. What I don't know is if it's caused by changes in the fan speed (which, you say it's audible over the normal fan, but that could qualify). It could also be different components making electrical noise, too.

  • It's definitely not changes in fan speed because it changes too quickly. Fan speed changes would at least be dampened by the inertia of the fan. What it could be is a HF signal coupling back into the PSU and moving the coils in the fan motor. – geofftnz May 25 '09 at 3:47

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