Recently purchased a 2012 Q7. In the last couple of days I have been noticing a loud whistling sound when I accelerate the car. I do have an appointment for next week (in about 3 days) at the Audi dealer but was wondering if it is safe to drive it until then. Has anyone had this problem? If yes, what was the cause? I still have factory warranty on this vehicle, do you think this is something that would be under warranty?