PC Coil Whine

Last month I converted my P4 desktop into a home-theatre PC. Using a soft paint brush I dusted down the old innards till they looked like new, and mounted them into a new case. After powering it up, I was upset to hear a screaming sound coming from my otherwise quiet PC. This would not do for a home-theatre PC.

Listening carefully to the motherboard I noticed two things. Firstly, the pitch corresponded with the workload of the CPU. And secondly, the sound appeared to be coming from the CPU itself!

Doubting my ability to actually hear resonating electrons within the processor, I searched the web for an answer. I found a post that suggested the chokes were responsible, but how?

Alongside the CPU are a couple of inductance coils. These little toroidal coils smooth out the power going to the CPU. My guess is that over time either, the varnish coating on the copper degrades, or the endless heating and cooling lengthens the wire by a tiny amount. Either, or both, of these causes would allow the wire a tiny bit of wriggle room. I further guess that the frequency of the AC power through the coil must be within the range of human hearing. This movement then translates into sound, as each section of the coil succumbs to the changing magnetic field of the section before it. By blowing out the dust I had inadvertently removed the packing that was preventing the coils from vibrating.

Close up photo of a motherboard showing two chokes covered in glue.
Is there nothing that hot glue can’t fix?

Now I’m not sure if my next course of action was the best thing to do, since it’s based on my earlier guesswork, but the PC has been running for nearly two weeks now and all is fine. I coated the chokes in a heap of hot glue, doing my best to contact as much of the surface of the wire as possible. I was pleasantly surprised when it worked!

If you know what actually happens to create the screaming sound and the subsequent course of action to take, then please contact me—I’m curious to know the truth of the matter.