Cars & acoustics? Lend me your engineering knowledge

[JtheJazzMan]

Im doing a soundproofing job on my car, I already have some dynamat type butyl rubber deadening sheets to put on the bare metal. But I also have lots of that heavy waste cotton padding cloth which I have noticed are sometimes on panels on older cars.

Any ideas on its effectiveness? Because its so cheap compared to the butyl sheets, Im thinking of putting it everywhere possible. Extra layers on the car interior floor, behind plastic panels etc. Any experience?

[hover]

expanding foam. non-organic batting. butyl sheets. your only real options. What kind of car we talkin here? You're never gonna get it dead quiet, half of that goal comes in the engineering stages. Any truly effective sound deadening you could do at the end-stage of the vehicle's production would come at the expense of functionality...