What is an effecient interior method of insulating home theater sound?

Question:I'm thinking of reducing the sound of my dvd home theater emitting through one or two of the side walls and the floor underneath, but I'm looking for interior insulating ways that mix up with the general decoration of the room and look neat. I got no problems with the cost as long as it is worthwhile. I've heard of insulating sponge-like materials that can be placed under the carpet. I think this should be easy to manage since I got carpet in the room, but what about the walls!

Answers:
There is a product called waffle-foam, that you put on your walls. We installed it on the walls of an advertisment studio to reduce echo and background noise. It normally comes in sheets 4'X6'. It isn't very stylish, but it will definitly cut down on escaping noise. Then all you have to do is hang fabric over the foam and you will have your own movie theater. Heavy cloth will collect a lot of escaping noise also. If you are worried about your neighbors complaining from the bass, place a small section of it beween you sub and the floor, it eliminates about 60% of the reverb on the surface the sub is in contact with. Good luck