--Go to a car stereo place and look for "Duramat" (IIRC). Basically
it's a peel-and-stick sheet of clay. It does a great job of deadening sound
and other vibrations. I've seen it used in doors, under hoods, etc to knock
down all kinds of noises; oughtta work a treat as a cheap-ish retrofit; no
fancy sandwich steel technology needed.

--
"Steamboat Ed" Haas : Steel, Stainless, Titanium:
Hacking the Trailing Edge! : Guaranteed Uncertified Welding!
www.nmpproducts.com
---Decks a-wash in a sea of words---