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PC noise mystery

  1. Sep 16, 2016 #1

    Stephen Tashi

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    I build new desktop computers every few years and I like quiet machines. Hard drives (to my ears) are noisy, so my last four machines have used a combination of solid state drives and spinning lap top drives. When I use any of these machines I hear faint sounds that I've always interpreted as the clattering of the spinning drives. The faint clattering is intense during boot up. After boot up, it often coincides my scrolling a web page up or down. It often happens when videos are played. Hearing the noise was frustrating because I interpreted it to mean that the computer was making heavy use of "tmp" files or swap space on the hard drive.

    However, I recently converted one of the machines so it now has only two sold state drives. I still hear the clattering!

    I used an electronic mechanic's stethoscope and determined that (on this machine) the clattering comes from the power supply. ( a Corsair TX750) . As I said above, the clattering isn't a random sound or a completely regular sound as one would hear from fan noise. To me it sounds exactly like activity on a quiet laptop hard drive. Some hard drives have a metallic "tinkling" sound. This sound doesn't have the metallic quality.

    One theory is that the sound corresponds to demands for power by the monitor or the hard drive activity LED. Is that reasonable?

    ( As I'm composing this post, the forum is scrolling various messages across the top of the page. The noise happens every time the message scrolls.)
     
  2. jcsd
  3. Sep 16, 2016 #2

    phinds

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    Sounds to me like you have some kind of weird cross-over coupling into your sound system. If you have a sound card, try either replacing it or if your CPU chip has built in sound, disable the sound card and use it. If you are already using the CPU's sound sub-system and have no sound card, get a sound card.

    Hm ... I see I've overly ignored you statement about the power supply. I should probably go to bed now.
     
  4. Sep 16, 2016 #3

    Stephen Tashi

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    Nevertheless, a coupling between circuits is a good idea. The motherboard has an onboard sound chip. The sound happens when there are no external speakers attached to the machine and the sound isn't coming from the speaker inside the computer case. However, I think circuits of any type can make faint noises.

    Right now, I'm using a different machine than the one I used in the original post. This machine has the same hardware as the other machine (including the Corsair TX750 power supply) except that it has one SSD and one spinning laptop hard drive. This machine makes the same noises in the same situations as the other machine. I used the stethoscope to determine that the noise comes from the power supply.

    I should emphasize that it's a very faint noise. I think most people wouldn't notice it unless their attention was directed to listening for it. They might not hear it even then if their computer case is good at blocking noises.
     
  5. Sep 16, 2016 #4

    phinds

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    Are you sure it isn't something related to the fans? I admit that sounds unlikely from what you've said but that's one of the first things I always look at.
     
  6. Sep 16, 2016 #5

    nsaspook

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    The sound is likely caused by capacitors and coils in the computer's voltage regulation circuit if it varies by CPU (load) related tasks.

    Nothing to worry about unless someone is hacking your computer.
    https://en.wikipedia.org/wiki/Acoustic_cryptanalysis
     
  7. Sep 16, 2016 #6

    Stephen Tashi

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    I'm sure it isn't noise from a fan.
     
  8. Sep 16, 2016 #7
    Just to entirely eliminate fan and sound card, those can both easily be disabled temporarily without harm being done.
     
  9. Sep 16, 2016 #8

    Stephen Tashi

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    There is no sound card. I know the sound is coming from the power supply. I may try jamming the power supply fan so it doesn't turn.
     
  10. Sep 16, 2016 #9

    Stephen Tashi

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    Worrying is not the point. I'm curious and fascinated by the phenomenon.
     
  11. Sep 25, 2016 #10

    rbelli1

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    The coils, transformers, and the ceramic capacitors in the power supply can make noise.

    As the magnetic field in the magnetic components changes any part that is even slightly loose or flexible will vibrate. Different loads will cause different modulations of the magnetic fields which can be heard if they or their harmonics are in the audible range. The ceramic used in capacitors is piezoelectric and the same applies. The effect is reversible. Loud sounds or other mechanical inputs can cause changes to the voltages produced.

    This is usually not a problem with digital electronics but can be problematic with analog signals. Higher end audio equipment will tend to avoid ceramic capacitors in sensitive parts of the circuit.

    BoB
     
  12. Sep 25, 2016 #11

    Stephen Tashi

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    On fedoraforum.org, member stevea gave a list of links to videos dealing with Corsair power supply fan noise. I haven't looked at all the links yet. The fan noise isn't necessarily noise that happens when the span is spinning but rather when it "tries to start spinning".

     
  13. Oct 25, 2016 #12

    NascentOxygen

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    But the monitor isn't powered by your PC's PSU, is it?
    In any case, can't you switch off the monitor while viewing that page with the noise-inducing scrolling?—the noise if it persists will then not be attributable to power changes in the display.

    Perhaps the scrolling uses Flash player, and loading and initialising a big software component might cause a spike in power needed by the processor?

    It is intriguing, nevertheless
     
  14. Oct 25, 2016 #13

    Stephen Tashi

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    That's a good idea. I unplugged the monitor from the AC outlet. The noise that corresponds to scrolling with the mouse still persists.
     
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