Attic Rock Box

Hello everyone I want to construct a space in my attic where I can play guitar and sing and keep the external noise to a minimum. My main concern is my girlfriend whom I live with. The amp I play with is 108db at 6 feet with a "C" weighting. I have attached a picture of the space I intend to build in. The finished floor space is 14.5 feet from left to right (in the picture). The bottom of the duct in the middle of the ceiling is at 8ft from the floor. Side to side there is 8ft of clearance where an 8 foot ceiling height could be maintained. The crawl space has no flooring and only a couple inches of fiberglass insulation. The attic has 4+ inches of Icynene in between its rafters and its studs. I'm assuming there is insulation under the flooring. There is no subfloor. I have a pile of metal studs in my garage, sheetrock, and mineral wool. So far my materials cost is zero. I will definitely need more to complete this project but as far as framing goes I know I'm most of the way there. My budget is 300-500 dollars. I'm not concerned about the internal acoustics of this space. This is not for critical listening, although it would be nice so any advice towards construction in that aspect would be great. Also, maintaining an 8 foot ceiling height is not imperative. What is the best way to approach the floor of the room I want to build? What method do you guys recommend for the wall/ceiling construction? Thanks so much! Marshall

have you done any measurements through the rest of the house and the outdoors? maybe sealing things up, adding some drywall, and an additional window with an amp riser to decouple it from the floor will be enough. then use rigid insulation to make some scatter absorption to get the room balanced.

Thanks for a quick reply Glenn! Are you imagining finishing the existing space or building a room within it? That being said, what's the additional window for? No, I haven't taken measurements anywhere else. My girlfriend was downstairs when I took the initial measurement and she said it wasn't so bad but she wasn't subjected to the merciless repetition I've been known to do if I'm practicing. Outside I'm not worried about. The guy closest to me plays drums sometimes and its not so loud in our house. I'd say our houses are 15 feet apart. The other guys house is over 30 feet away for sure.

the window would be to add another layer since a lot of sound can exit the window and thus be heard in other building or downstairs. i'm just thinking mass on the rafters and walls. maybe decoupled with clips and hat channel or not.

What if I built a room within my attic? I think I have enough materials to do something like an 8x8 space (interior dimension). I'm just confused about the best way to decouple something like that from the attic floor. From what I've read around here, I've seen a few methods for wall framing to reduce sound transmission, but not much that explains how to decouple the deck that I would build this room on. Am I missing something? Thanks again Glenn!

Ha! Nevermind, after searching through some more posts I think I found what I was looking for, sorry about that!