During our Malibu Run when I was running around 10 to 15 MPH and hitting the center road reflectors and my window was opened I noticed to hear a clanking sound somewhere under the drivers seat or behind. I am not sure what it is but now that I am aware of it everytime I am driving slow with windows opened and hit those middle road reflectors or some big potholes I hear the clanking sound again. It seems like something like my exhaust is making that noise. Does anyone know or experience something like this? I am planning to ask my dealer but I don't think it is something that needs immediate atention so I will just wait till my first oil change but if someone can tell me about this I would appreciate it.