I have a 2013 Accord Sedan, and I have recurring sound that I hear usually when the car is idling, but sometimes even when it is moving. It actually sounds like plastic behind the rear seats is vibrating against the rear window. I read somewhere that it could be the cover on top of the 3rd brake light, so I covered the top with a felt pad, but it didn't make the sound go away. I don't really see any areas where any plastic is touching the glass or close to, so I'm thinking it could be something loose. I also removed the plastic covers on the seat anchors behind the headrests thinking that could be it, but that didn't do anything either. Anyone have any experience with this or have any ideas before I randomly start taking the whole rear apart trying to find things to tighten?