I have a Malibu Maxx and had a rattle that got progressively worse as time went on. It was at the base of the windshield. It started normally about 40 and went away about 50.
Well one night it didn't matter what speed, it buzzed all the time. So I called the dealer and left a voice mail for my salesman. I asked him to pick up the car that monday and not to bring it back until the rattle had been resolved or the car had been destroyed.