I have a friend who has an electric drum set in an apartment. All parts are electronic so there is no noise when the set is played unplugged. But when run through an amp, the sound gets out into other rooms. To soundproof, he put up a set of walls and floors/ceilings inside the room and their is dead air space in between the room inside the room. It's a room within a room. He is a carpenter so he knows how to build anything. Everything is cut out except for some of the bass response which leaks to other rooms. Is there a better way to baffle the sound between walls of the inner room and the surrounding exterior room?