acoustical damping

I've been looking through various posts concerning noise damping on the 123 diesels. I've seen alot of testimony about how nice the MB hood pad is. Does anyone know what its made of? Does MB (or its aftermarket copycats) post any data as to acoustic loss factor or actual decibel reduction?

I've seen the posts about quilted fiberglass, though information concerning its effectiveness is purely anecdotal (not that stories are bad, just hard to compare). Anybody else out there with an oscilloscope and a microphone?

And I was just curious if anyone has tried acoustical foam - and what your results have been. I'm an engineering student at Boise State, and I've seen some pretty impressive acoustics projects demonstrating the effectiveness of a little foam. In one project, a student (Way to go Todd!) was working with Electrolux, in an attempt to make vacuum cleaners less annoying. Less than a dollar of foam (correctly placed) cut the noise levels in half.

If anyone has any ideas or information that would add to whats been posted in the past concerning acoustic damping (anecdotal or otherwise) - thats what I'm hoping for.