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I'm hearing a whine coming from my laptop, it's quite noticeable and sounds pretty much like this but without the loud clicking.

http://www.youtube.com/watch?feature=player_detailpage&v=OjINGudIi-s#t=37s


Does anyone know what it could be? I've closed all my apps one by one and it still goes on, I've restarted but it's still there. It's quite annoying, any help would be appreciated :)

Does it come from the speakers?

I would document it heavily (record a video showing your Serial number on the screen and pan down to pick up the sound of the noise) and call AppleCare. They'll likely have you install diagnostic software and diagnose remotely.
 
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