Where does the sound come from? Your headphones, speakers, etc. Does it ever happen when your machine is off? You mentioned you only have wired audio peripherals - perhaps someone is playing a prank on you and has connected some kind of device inline.
Where does the sound come from? Your headphones, speakers, etc. Does it ever happen when your machine is off? You mentioned you only have wired audio peripherals - perhaps someone is playing a prank on you and has connected some kind of device inline.