Yes, it is caused by the vibration of the cover behind the rear seat backs vibrating against the rear window. Watch Carefully, you will see the rear window "flex" in severe bass notes. If you are mechanical -- remove the rear seats -- pull up on the front of cushion bottoms, and disconnect the seat sensors. DON'T Disconnect the HIGH VOLTAGE Connector under the left seat Cushion. Pull straight up on the seat backs and remove (They are slotted on each side and pull straight upward will remove them). You will have to unscrew the center panel/cup holders (look under the rubber cup holder inserts for the screws. This will expose the screws holding the rear ledge that cover the sub woofer. The noise is caused by the vibration of the rear (nearest the window) of the ledge vibrating against the window. Once removed, apply a adhesive insulation foam on the point where the window and the rear ledge meet--the perfect placement is on a slight 45 degree angle. Make sure the foam presses against the window slightly before reinstalling. A possible "quick" method is the use a weather stripping and press it between the space between the window and the rear ledge -- be careful not to scratch the antenna and defrosting film on the rear window. It is difficult to "hide" the insulation with either solution, so pick a foam close the the interior color of the car. Removing the seat backs and ledge is the most effective.
It is not difficult, but you need to be familiar with removal of panels from cars. Otherwise I would recommend you take to the dealer/service guy and have it done.
