depends on what source I'm using, I can't hear any of my "stand alone" source units, excepting the VCR or LD player (if its spinning an LD, the VCR you hear the mechanical noises, and the LD player just displaces enough air when it spins up that you hear a light brushing air noise if you focus in on it)
the computer has fans, which are audible, but I'm so used to background noise that I can't sleep comfortably without some sort of fans on (be it the computer, or something else with a light fan)
quite comfortable listening environment imho