I had my wife ride in the back seat of the car and drove down the interstate to find an annoying buzzing sound that seemed to be from around the rear coupe windows. She put her finger and press up about 5 inches back from the front side of the window and the sound stopped. I hope this makes sense since i don't have a digital camera. She is pushing up toward the roof on the car inside the window cavity. Then once we got back home, I tapped the plastic around where she pointed and found a spot that sounded like plastic hitting metal or something. So I took a leather strap with about 1/8" thickness and cut it into 3"-4" strip. One strip for each side of the car. I bent the very end of each leather strip and pulled down the plastic with the head of a screw. Then starting with the bent part of the leather, slipped it up behind the plastic to make a spacer between the plastic and whatever it was buzzing against. Buzzing sound gone