[Weasel9992]

1.) I've seen some pretty small rooms work well, but the smaller they are the more treatment they'll require. The composition of all the surfaces plays a big part here...i.e., sheetrock is better than cinderblock (but not for the question #3). If possible avoid rooms that are a whole cube (8x8x8) or rooms where one dimension is the multiple of another (8x16x16). A good starting place might be 8x11x15...something like that. Of course, an 8' ceiling isn't great either, but I'm assuming that you won't have much choice there. If you do end up with an 8x10x10 space, it's not the end of the world...it just needs to be treated well.

2.) Ground floor would be best I think...less places to transfer noise to. Composition is the tricky part. Sheetrock has better absorbtive properties, but concrete/cinderblock has better isolation properties. If it were concrete you could always install a layer or two of sheerock over it with an air gap between the layers. Do you know whether concrete construction is an option? I suppose it might very well be in a cold part of the world.

3.) Isolation is the tough part. Normal construction methods will allow everything under 100Hz or so to move through it like it was paper. The only way to stop it is to add mass (thicker walls filled with sand and two layers of sheerock with an air gap, for example); acoustic treatment will help a little, but won't provide anything like "isolation". Floating a room is always an option, but it can be very expensive and it's really not designed to eliminate noise transfer from inside the room to the outside. It's really meant to do just the opposite...avoid transfering noise from the outside of a room to the inside. The added mass of a couple of layers of sheetrock would help a lot though, no doubt....if you monitored at reasonable levels in a treated room that might be enough to keep you out of hot water with the neighbors.

Hope that was helpful. Let me know if you have any questions.

Frank