I live on an apt and got the ok from the building owner to build a band room in the basement. It is only a two unit building - my wife and I are on the second floor and there are tenants on the first floor. I play guitar, my wife will either be the bass player or keyboard and one of the first floor tenants will likely be the drummer, so it doesn't need to be 100% perfect sound isolation but I'd like to be able to play loudly on my own at times without the first floor people being bothered. So here's a sketch I made yesterday to get the ball rolling. (the existing building materials are light gray lines, new materials dark lines) The room is 9 feet at the widest point and about 15 ft long. As you can see three of the four of the walls are not attached to the structure. I plan to use multiple layers of thick drywall for mass and to set a ceiling on top that is not connected to the floor above (not sure how to do this yet). My question right now is: will securing the room to the concrete floor and exterior masonry wall transfer much vibration up? The wall is composed of a concrete foundation about 3ft tall and brick above that. I've read a lot about sound travelling through frame walls but haven't seen anything about masonry. I'm not even sure if any of this is financially feasible yet. I'm just starting to gather information. Thanks.