Rt rear rumble-body,not a rattle. 40,000 miles on 2005 Acura TL

rt rear rumble, through rear door, appears to come from trunk. Everything in trunk is secure. It virtually disappears after car is on the road. Acura dealers hear it but don't know what it is.

Asked by for the 2005 Acura TL
The only way they will find the noise is remove the interior trim in the trunk and have someone get in the trunk and try listening for the noise with the trunk lid open and closed, and or move around a mechanic's stethoscope to isolate the source of the noise.