Rattle in rear driver door panel
 

there is an annoying rattle in my rear driver door panel when i hit decent size bumps. i took the panel off to see if the linkage for the door lock was hitting the panel. i placed some foam tape on the door frame behind the door lock knob [it's metal, looks like it was hitting the metal door frame] and i also taped some cloth around the door lever cable which is exposed between the door frame and the panel. this did not solve the rattling. anyone have any clue to what might be creating the rattling sound. it's emanating from the door lock knob area.