Dampening will help some with sound but you also want to look at something like ensolite. The only problem is that it takes a bit to air out and get rid of the smell.
http://www.raamaudio.com/

Its light and provides a barrier. Its different then things like dynamat that mass loads the metal and is more for preventing resonance rather then getting rid of road noise although it will still help.
http://www.b-quiet.com/vcomp.html is another place to look. i believe even cascade has materials similar.