there is a strange noise that randomly occurs in the morning in my house. It sounds like a jack hammer. It is most prominent in my master bedroom bathroom, where there is a vent on the low part of the wall, but I can't figure out where it's coming from. My furnace and ac are not on and haven't been for days! The only other thimg I can thinl it would be is a woodpecker somewhere? Any idea what it is?