This is probably a dumb question, but I'm asking anyway. In my iGT with the Bose speakers, when there's nothing playing, or the volume's turned all the way down, or it's muted, there's a low hiss coming from the speakers. This happens on all inputs. Is this simply normal speaker noise? It's quiet enough to be covered up by road or engine noise, but I figured I'd ask just to be sure this isn't unusual or something to keep an eye on it worsening.