posted on Dec, 13 2013 @ 04:07 PM
From my own experiences, I have a few theories.
1) interference from a radio wave (i.e. Cell phone interference), when your about to get a email, text, phone call (especially a phone call), etc.
your speakers will pick up the interference, but only slightly.
2) Bad connections between 3.5 mm and the socket on the computer.
3) Brown outs, power surges, (i.e. Power fluctuations).
4) Just having them plugged in and no sound going to them will have a little bit of static from the flowing elections powering the speakers and what
is being sent through the audio connection to the computer. ... I would guess its a bit of all of them combined.
Without knowing more information, this is all I can give you. Hoped this helped.