This has always bothered me. It states in the spell invisibility that you are not magically silenced, and other factors like walking through puddles, can reveal your presence. I would argue that the above only applies to the vision part of perception. for the hearing part, should the person invisible use stealth to move the perception would be just his stealth and 0 for being invisible, plus distance. If he is moving in things like dust, snow, water etc. then he would leave tracks, unless he has way's of avoiding making them. If the invisible creature move without using stealth, then it would only be distance for the sound part.
Thanks, Walt
