Welcome to the group.. AT Idel I agree with the other exhaust leak but more then likely the rattle sound could be the jack vibrating and the plastic floor /jack cover echoing the sound.. Speakes make weird noises as well when broke as was also mentioned. In your drieway open the hatch and start the car, if you hear the noise put your hand on the floor and see if that helps... Please post what you find,you will be helping other noobs like me :)