Hi - My daughter purchased a used 2008 Cobalt LT (4 door). When driving, a lot of road noise can be heard through passenger side front door; the driver's side front is quiet. It seems as if the noise is coming through the speaker cavity. If you place you hand over the speaker holes, the noise is significantly muffled. Should there be a piece of insulation between the speaker and the outside metal door? I'm not sure what's missing which would allow the noise to project into the car interior? Any suggestions? Thanks.