how to make interiour noise quiter

hey guys, i just wonder if its possible to make interiour noise more quite cuz im driving an integra and also have loud muffler, so its too noisy to drive on highway so i was thinking maybe there is a way. what i was thinking maybe put some wool under plastic covers and on doors, under panels rip stock plastic cover and install some thicker one. theoretecly it should block sound from outside but before ill sdtart doing it maybe someone have some advise for me :) thank you

I know some people who use Dynamat, works ok.

whats that? lol and can i get it at home depot?

Not at home depot, Best buy will have it, there should be other products similar to it. its just a roll on mat that reduces noise, i think most people use it in their trunks on the botom and sides to reduce vibrations.