whining noise from laptop speakers

Hi all, My HP Pavilion laptop has started making a whining noise through the speakers. It is most annoying when the CPU fan starts spinning, but I can
also hear it when the CPU fan is off, the difference is the noise is intermittent, maybe when the hard drive arm moves to read something or when the RAM is written to. I know it's coming from the speakers because I can mute them, thereby suppressing any whining noise.
What is this? Is it electrical interference? How can I get rid of it?
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someone_else wrote:

Low internal supply voltages. The sound electronics starts misbehaving because of that.
Or a decoupling electrolyte near the soundpart has degraded, with the same bad behaviour.
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wrote:

Another possibility may be interference. Try to see if there is a mobile phone or any other radio device that could be responsible.
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On Sun, 22 Feb 2009 13:28:53 -0800 (PST), Boris Epstein

Come to think of it, on one laptop I ran a latency test and found the broadcom PCIe wireless card, or it's driver, was responsible for a bit of audio crackle, but this seems a different noise than just periodic crackle. Disabling it in windows' device manager removed the problem, but in this case I think a bus/timing issue rather than RF pickup.
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On Sun, 22 Feb 2009 00:30:17 -0000, "someone_else"

Go to the volume screen and try muting the various inputs to see if it can be isolated to one of them.
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someone_else wrote:

Have you checked the mixer control panel for the sound device ? Are all the input channels, except the one you're interested in, muted ? The Mixer panel may have a "record" and "playback" section, and sometimes the panel attempts to deceive you by hiding some of the important bits. Some computer audio devices have a "what you hear" option, which loops an input, back to the speakers, and that might result in additional unexpected noises. It is even possible some piece of audio software (Skype? or an "in-game audio option" ?) may have reconfigured the audio for you, in an unacceptable way. Check what you've installed lately, for something audio related.
Paul
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Thanks to all for your suggestions they helped me find and fix the problem in:
XP control panel

This setting may have been changed by recently installed language software, or by me trying to route sound files through Second Life, or maybe it was set already and I just recently become intolerant to this noise.
thanks all!
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Thanks to all for your suggestions they helped me find and fix the problem in:
XP control panel

This setting may have been changed by recently installed language software, or by me trying to route sound files through Second Life, or maybe it was set already and I just recently become intolerant to this noise.
thanks all!
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On Sun, 22 Feb 2009 00:30:17 -0000, "someone_else"

Has anything about the system or use changed, particularly software or ambient room temperatures?
Generally this is noise on the power rails, that it didn't happen previously leads me to suspect some variable has changed causing a different amount of power consumed.
Is it possible you had the noise all along but now the volume is set higher than it used to be so you are hearing it louder? Noisey audio on laptops is far too common, but normally it is there all along not appearing only after some time.
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