Chris, I am happy to delete this if you don't want it in here. It is difficult to undo the brain-washing that has occurred over the last few decades, but I am trying
---------------
http://www.expeditionportal.com/for...ishna-Operation-K-I-S-S?p=2126691#post2126691
First, don't buy anything that says Dynamat on it.
Now that is out of the way, you have a few options:
To properly dampen sound, requires a bit of engineering and a bit of planning. Covering the inside of your Jeep, van or Honda with MLV (Mass Laminated Vinyl) is not the answer to proper sound deadening. It is the answer, however, if the question is, "how do I waste a lot of time and money?"
See if you can find someone in your area like these guys, they know sound deadening:
https://www.sounddeadenershowdown.com/
You may need a product like Spectrum's Sound Sludge in one place, LLP (Luxury Liner Pro) in another place and two layers of 3M's Thinsulate, which is hydrophobic, non-woven, non-linting polymeric micro fiber, in another. There is NO one product that does everything and there is no formula that fits every car or truck. Each product has a job, so to speak. An all terrain tire sucks on a race track and a drag radial sucks in the mud. Both are tires.
Think of the difference in sound between a door slamming and someone walking on a hardwood floor in high heel shoes. What about a screaming child in the next camp site over compared to miles of rough pavement?
More is not better, covering all the walls, floor, ceiling and doors in heavy sound deadener will certainly attenuate some sound, however the idea is to change the resonant frequency of the panel with different materias, as I understand it. Sound is transmitted by vibration at different frequencies, so the goal is to minimise the sound transmission over a broad spectrum, whicih is not a cut and paste job, completed in an hour after work. Take your time and do it right and you will enjoy your van much more.