Wes and Rod, I am considering cutting my basement floor concrete slab in order to isolate a section of floor from the rest of the house. I have a "control joint" crack along one section of the floor, and I have performed a very simple & crude test to confirm that this crack does create significant isolation between the two sections of floor divided by the crack. However, my main concern is not isolation from one area of the basement to another, but from the basement to the main floor of the house. So, the sound travel path of concern is from the basement floor to the basement walls to the main level floor joists (the basement walls are cinder block on top of the concrete footer, and the floor slab was poured over the footer and butts up to the cinder block wall). It seems that in order to de-couple this path I would need to cut the concrete floor far enough away from the block wall to disconnect the floor slab from the foundation footer. I think this would cause me to loose about 6 inches on each side of the room enclosed by a basement wall (3 sides of my room would be affected in my case). So, my queston is - will the isolation improvement beteen the basement floor and the main floor be enough to make it worth loosing 6 inches on 3 sides of a room that is approximatley 24 feet by 14.5 feet? (I will already be building a "room-within-a-room" with its own ceiling separate from the floor joists to maximize the air-borne sound transmission to the main floor) Thanks!