I showed initial steps I took to add some sound deadening to a diesel Ford Excursion. It's a loud car; the 7.3l diesel engine exhaust could definitely use some muffling.
In this -part II- I'll show how I laid self-adhesive aluminum/butyl mat over all the sheet metal in my car's cargo area. I covered that first layer of sound deadening material with a glued-down sheet of ensolite foam to absorb yet more sound energy.
I laid down a double sandwich of those same materials on the floor. Per advice from an expert, Rick McCallum of http://www.raamaudio.com
, doubly covering the floor will help most with blocking out sound from under the vehicle.
I also used expanding polyurethane foam to fill in some huge and undoubtedly resonant voids inside my truck's body panelling.
I understand that most people who go to this amount of effort with sound deadening do it for car audio reasons. My primary intent with this project is simply to quiet the interior of the car.