Has your pc ever stuck or freezes?
I mean yes, if a computer got so busy (especially when running a heavy program or downloading heavy source), strange noise usually happens when you move your mouse. Its like ur computer got so busy and running a lot of juice
My previous statement could not be ur problem. Ur speaker is fine.Does a computer need more rams? or adjustments at audio setup...
try 'run' dxdiag, to test your sound card. im quoting whatever i know.