jeez – you would have been better off just finding a used whisper booth. assuming you can’t get anything of that quality, then hockey pucks, pac pipe and moving blankets will be your friends. It’s ugly as hell, but it will sound better. First, you’ll need a floor as part of the enclosure, you can’t share the floor of the room that it’s in. You can then put the booth up on a series of hockey pucks spread around under the booth floor, with the hockey pucks sitting on another piece of plywood (at least 7 ply would be nice). That way you’ll have a bit of decoupling from the main floor. Use the PVC to attach to the walls (use various plumbing attachments from home depot etc) and you can drape the moving blankets from the PVC piping. Get as much wall coverage as possible, down to the floor. The floor should have a rug or carpet as well. Same as the ceiling. You just want to get the walls to be as ‘unparallel’ as possible, so if the blankets are bunched up, and have folds etc, that’s good for diffusing sound waves. If you have room you could get some cheap auralux foam bass traps for the corners, but those won’t help with super low frequencies. Better than nothing. There’s a lot of info putt here about this stuff – check out randycoppinger.com as he has some blog posts about building vocal booths that might help.