i'm a studio owner here in la and i can tell you that the very best products that you can use for soundproofing are lead sheeting and sound deadening board. the lead sheeting is very very thin and not very expensive. you may have to look around to find someone that carries it. the sound deadening board can be purchased at most lumber yards. the real secret however is; both materials for optimum performance must be glued into place NOT nailed. the nails will help to transmit any vibrations(ie. sound)thru the walls. heavy duty construction adhesive that you can purchase in tubes works well.