Hissing (whining, screeching, buzzing) noise when processor is idle

Question

This is a problem observed on other models of Dell laptops as well (see the thread 'Inspiron buzz'). Also it seems to have been a very hot issue a year ago or more, some people were happy with workarounds like disabling the USB hub, butthis doesn't work for everyone. So I decided to reopen it to see whether there is any new development. The problem is that the laptop produces some sort of buzzing noise, sometimes described as 'hissing' or 'whining' or 'screeching' in hundreds of Dell forum help requests. The noise is not related to HDD, fan, soundcard but rather comes from the internal power supply. It is produced probably by worn-out / cheap transformers (ferrite) when the current flow changes due to increase /decrease in power requested by microprocessor. The noise is not present on Windows 98 because this OS keeps the processor busy all the time (the drawback is that the fan will come on much more often and the battery would not last). But it seems like modern OSs (ACPI) would make use of HLT instruction to force the processor in a low power mode to save the battery life and also to keep the cooling fan off. It is obvious that when the processor is busy the noise is gone (this can be verified in Task Manager, whenever the 'idle' task is taking 99% of processor time you will hear the noise, but not when some other task is active). I even found a way to make it stop and then make it obvious when it comes back, it's dealing with windows size adjust in some applications (Acrobat Reader). Although the noise is not loud (not audible when the fan is on, or when a CD is spinning) it is very annoying because one would expect complete silence since the computer is not doing anything. More, moving the mouse cursor on the screen would make it louder and change tonality, which could become intolerable. It is worth mentioning that I have tried all suggestions found in this forum, like USB hub, latest BIOS, latest drivers, disabling Power Management. I actually removed all components except motherboard and videoboard and the noise is still there. This message is being reposted since I haven't got any feedback the first time. Anybody experiencing similar problems please reply, maybe together we can find a solution. I would appreciate some insight from Dell engineers in this forum, as it is obvious that this is not an isolated case. My Latitude C600 is out of warranty and I'm not getting any help from phone support team. Do you believe that the power supply can produce this noise? Regards, Adrian

AussieChris · Answer

Hi,

Not quite what you are after, but I have had CPU's causing noise. The older small PCB style, I dont recall the later style doing so.

Regards Chris

dolphindunes · Answer

Have you seen your cat lately???

AussieChris · Answer

I dont have a cat, I have a brain, it may not be worth much, as it's been used a lot.

adsp · Answer

Unfortunately, I have to live with my 'cat' and seems like the only chance I've got is to get used to it. The other day I've just found another 'miaou'! Unplugging the laptop from the AC power supply, a very high pitch continuous note has come out of the unit for minutes (low amplitude though). The funny thing is that there was no battery plugged in!!! Adrian

Locked Topics – Laptops General

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