I have had this noise for a while now and I really haven't been able to pinpoint it. Its somewhere near the driver side top dash, near that vent on top. I tried replacing the vent and that didn't solve it. I don't know if it's coming with in the dash or what. Nothing fell inside the vent or anything, it sounds like plastic/urathane vibrating. Any help would be greatly appreciated as i randomly punch the top of my dashboard to try to stop it lol.