Cutting out background noises isn't really my concern. I write/record heavy metal, and basically I need to yell without my room mates and/or neighbors calling the cops on me. So I would like to build a small sound isolation booth. I was thinking about 3' X 3' X 6', with hinges between the walls so it would be easy to break down, and thus portable. If I built it with plywood for the walls, with a few inches of appropriate foam on the inside (and on the ceiling of course), would this do the job of cutting down sound levels? Is there something I could put on the outside of the walls to help, like dynomat? I have a carpeted floor, for what it's worth.