Gary, did you find out what the sound was?

I feel fortunate that my 85' 380SE still has a quiet, rattle, pop, tick and squeak free dash panel, despite 265K miles. The only noises I have is from the dash cover installed on the dash pad. It sometimes makes "scrunching" noises. The only other interior noises I have is the wood trim on the door panels occasionally make a "scrunching" noise. Its not rattles or squeaks. Its like no other noise I have heard in a car before, but it is not a bothersome noise like rattles are. My car has always been a southern car and I think it is where the sun has hardened the trim on the doors, hence the scrunching. I have been using "303" protectant on them and the noise has been getting quieter and quieter.

The 90' 300SEL I test drove last summer with 174K had already developed this noise on one of the rear doors, but oddly, it also had a lower center dash rattle, but the owner had added a CD player there, which may have caused that.

Anyway, it sounds to me too like it may have been something with your speaker.