I have done several oil field trucks in west Texas. One of the problems with the sticky matting is on roofs and firewalls the stuff sometimes falls off. It was not originally designed to be used in autos but that being said, it does do a good sound deadening job in certain areas, like door panels, cab walls and rear walls by reducing metal vibration. The adhesive is not designed to hold it own weight upside down like in headliners. It was originally designed as a roofing material to be stuck down, not up, and can be purchased thru Lowes for about 100 bucks for a 3' wide by 33' long roll. There used to be a guy in Austin that sold it for cars. He was buying seconds from the manufacturer that did not pass QC for roofing and he sold it quite cheaply on EBAY for awhile.
The neoprene foam does both jobs in one but can get pricey. I have even used sound reduction foam like used in studios that looks like egg crate and it works and is not as expensive as neoprene foam. Install wavey side to the inside.
The most economical is the quilted stuff but must be glued in place with contact cement.
