I wanted to add some sound dampening to the roof after adding subwoofers and updating the audio in my Toyota Tacoma. After doing a bunch of research and not wanting to spend hundreds of dollars on Dynomat I decided to use a product called Peel & Stick. It cost about $17 for a 6″ by 25 foot roll. It was relatively easy to install, I used a heat gun to warm each piece prior to placing it down. I used a 2 in 1 rolling pin to help remove any air bubbles. If you are having rattling issues or you just want to make eliminate road noise I highly recommend this stuff as a cheap sound dampening alternative.
Cheap Sound Dampening Alternative: