# High-frequency computer noise, cause of… **URL:** \ **Category:** Factual Questions\ **Created:** [July 2, 2007, 4:58pm UTC](https://boards.straightdope.com/t/high-frequency-computer-noise-cause-of/410246 "2007-07-02T16:58:04Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Janx](https://avatars.discourse-cdn.com/v4/letter/j/b9bd4f/32.png) [@Janx](https://boards.straightdope.com/u/Janx)\ **Post date:** [July 2, 2007, 4:58pm UTC](https://boards.straightdope.com/t/high-frequency-computer-noise-cause-of/410246/1 "2007-07-02T16:58:04Z")
My Computer is making a VERY high-frequency “whistle”. It sounds almost like a silent dog whistle. This is not a “hum” or a “buzz”. The origin does not seem to be mechanical, (no fan noise, dying hard drive etc). It is not coming from the monitor; it is coming from some other component in the case itself. I have opened the case and let it run, and still cant nail it down. I have vacuumed the dust out, tightened the various boards in place, and changed the power settings, still no change. The noise makes my girlfriend’s teeth itch; she can’t be in the room while my computer is on. I can hear it but it doesn’t bother me, but I would like it to stop. Any ideas? Oh yeah, Athalon 1.6 ghz 1 gig memory 128 meg Nvida video windows XP Thanks! ---
**Author:** ![casdave](https://avatars.discourse-cdn.com/v4/letter/c/c6cbf5/32.png) [@casdave](https://boards.straightdope.com/u/casdave)\ **Post date:** [July 2, 2007, 5:07pm UTC](https://boards.straightdope.com/t/high-frequency-computer-noise-cause-of/410246/2 "2007-07-02T17:07:19Z")
This will be your power supply unit. These units work using a Switched mode supply.The sound you hear is the power device inside being turned on and off at around 15KHz up to around 22KHz. You probably cannot hear this sound directly, but you may well be able to hear one of the harmonic components, because these things produce lots of noise across the frequency spectrum due to the way they operate. [http://www.mcitransformer.com/i\_notes.html](http://www.mcitransformer.com/i_notes.html) [http://www.williamson-labs.com/powersupply.htm](http://www.williamson-labs.com/powersupply.htm) > **[Switched-mode power supply](https://en.wikipedia.org/wiki/Switched_mode_power_supply)** > > A switched-mode power supply (SMPS), also called switching-mode power supply, switch-mode power supply, switched power supply, or simply switcher, is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently. > Like other power supplies, an SMPS transfers power from a DC or AC source (often mains power, see AC adapter) to DC loads, such as a personal computer, while converting voltage and current characteristics. Unlike a linear power supply, the pa... ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [July 2, 2007, 5:19pm UTC](https://boards.straightdope.com/t/high-frequency-computer-noise-cause-of/410246/3 "2007-07-02T17:19:19Z")
It can also be the motherboard, or any other printed-circuit board, that has a DC-DC convertor on it, which behaves like a small switching power supply. ---
**Author:** ![Janx](https://avatars.discourse-cdn.com/v4/letter/j/b9bd4f/32.png) [@Janx](https://boards.straightdope.com/u/Janx)\ **Post date:** [July 2, 2007, 6:20pm UTC](https://boards.straightdope.com/t/high-frequency-computer-noise-cause-of/410246/4 "2007-07-02T18:20:10Z")
Yep, seems to be the power supply, thank you! Now what? Do I need to change it out? Take it out of the case and smack it around a little? Is there a filter I can get? Change girlfriends? Thanks again. ---
**Author:** ![casdave](https://avatars.discourse-cdn.com/v4/letter/c/c6cbf5/32.png) [@casdave](https://boards.straightdope.com/u/casdave)\ **Post date:** [July 2, 2007, 8:36pm UTC](https://boards.straightdope.com/t/high-frequency-computer-noise-cause-of/410246/5 "2007-07-02T20:36:53Z")
It may be full of dust and crap, the extra heat tends to make the electronics work harder. Its not always a great idea to unfasten the casing to clean it, best is to blow it with air at low pressure. ---
**Author:** ![MysteryFellow63427](https://avatars.discourse-cdn.com/v4/letter/m/a88e4f/32.png) [@MysteryFellow63427](https://boards.straightdope.com/u/MysteryFellow63427)\ **Post date:** [July 2, 2007, 10:47pm UTC](https://boards.straightdope.com/t/high-frequency-computer-noise-cause-of/410246/6 "2007-07-02T22:47:42Z")
[QUOTE=Janx] Yep, seems to be the power supply, thank you! Now what? Do I need to change it out? Take it out of the case and smack it around a little? Is there a filter I can get? Change girlfriends? Thanks again. [/QUOTE] You’ll probably need to either change the power supply or the girlfriend. Power supplies are in the neighborhood of 75 bucks\*. Your call. \*I’d do some research to find a “silent” one–I believe some of them are engineered to produce less ambient noise.