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Replaced motherboard; speakers; put in an additional fan; but this did not stop the static noise. This was done by inhouse tech. support from Sony. If i turn my speakers mute; the sound is still there! Can't hear it through headphones. I was told it is feedback noise! Now I'm suppose to send my $2,000.00 computer through the mail to get fixed? I'm terrified it'll come back in terrible condition during the travel time? Help?

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what laptop model, exactly? What OS? Have you made any changes recently, hardware or software-wise? –  studiohack Jul 16 '11 at 20:03
    
Are you sure it's not simply the disk drive. The disk drive makes a sort of buzzing sound (very quiet) when being accessed -- you can "correlate" the noise with the flashing of the disk light. But a loud buzzing sound is apt to be the fan. Sony had a bunch of bad fans (actually, the wire feeding the fan was poorly secured and banged against the paper-thin fan housing) and they have a recall on it: esupport.sony.com/US/perl/… –  Daniel R Hicks Jul 16 '11 at 23:00
    
I'll add that I sent in my Sony laptop (list price only $700 but worth thousands to me) for the fan service and it arrived back in good order eight days after I sent it in. (This was in the US.) (Dealing with the Sony people on the phone, however, was a real pain -- 15 minute wait times, etc.) –  Daniel R Hicks Jul 16 '11 at 23:03
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2 Answers

It can be a few things, depending on exactly the type of sound.

1. Coil (possibly also capacitators) whine These are known to sometimes resonate under specific currents. It's a defect for sure. And the laptop can (should) be returned for the problem to be fixed. Here's an example of type of noise (starts at 00:20 mark): http://www.youtube.com/watch?v=SeahtqeTrGo

How to know if this is the problem? Because the noise is actually dependent on current draw, the noise should vary in intensity and even go away (and come back on) when forcing the computer between idle and load conditions. Loading games that ask the graphics card to draw more current (and consequently the PSU), should, if this is the problem, alter the intensity, remove or generate the noise.

Another, more extreme example: http://www.youtube.com/watch?v=f-qdWVk5wzs&feature=player_embedded

2. Bad grounding This one is common if your electric connection or the device (computer itself or power adapter) aren't properly grounded. Here's an example of the type of noise: http://www.youtube.com/watch?v=yfmMlCfyxxc (starts at the 1:40 mark)

This noise affects speakers, internal or external, but only if you are sure this isn't a problem originated by your own electrical installation. Trying the laptop on some place where you know grounding is properly installed is a sure way to know about this. But if this is caused by your electrical installation and you have no way of fixing it, you can acquire a ground loop isolator. These sell at peanut prices: http://www.google.com/search?q=ground+loop+isolator

Here's another, more typical, example (starts at the 00:30 mark): http://www.youtube.com/watch?v=CvMHmgFjf_U

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Thanks none of those sounds. My laptop is three years old; I use it 6 months out of a year. It's wireless and it just started to happen. Been plugged into the same surge protected all this time. It does comes and go. If I could attach a MPD somewhere you could listen to the sound. thx –  joanna Jul 17 '11 at 0:56
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Just Disable "Listen To Device" In Recording Settings From Your Sound Manager On Your PC/MAC

check out this picture

http://i.stack.imgur.com/2qWPg.png

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