It can be used that way. Dynomat's main purposed was to stop your car from rattling apart when having large stereo systems in the car, as well as deadening the sound of racecars as well. This material will greately reduce the exterior noise of a cars interior therefor providing you with a quieter ride.
However, it tends to be heavy, so loading your car down with it will add a good amount of weight. Most people dont care, but Im a poor boy trying to make my car faster any free way possible!
I was given a Dynamat door kit, I went to install it and I ended up postponing the project since I wasn't sure if the foam needed to remain where it's at...Does it provide any type of support for the interior panel at all? My audio system isn't anything fancy, but the doors sure do rattle a lot when I get the music going.
Dynamat will NOT replace the foam in the door panel. While the foam does help with sound insulation, I found it also helps heel the panel from flexing too much. If you remove the foam, you'll likely get a creaky panel whenever you put your arm on it.
You can cut off the plastic sheet glued onto the door - that's there for sound insulation only.
I personally recommend Cascade Audio for sound insulation - it's thinner, molds to the shape of the door better, and dampens the sound better. Though it is more expensive.
I once had a small car. It had no insulation in the door panels and sounded like tin when shutting the door. I attached dynomat to the inside of the metal door and shut like one them marcedees every since! Yes it works! I like it.