About 8 months ago, I built my first vocal booth. It was made with some 2x1x3 beams and insulated with rockwool then covered with moving blankets. Then the walls were put together in my spare bedroom. The booth was ok. I had a decent noise floor most of the time. I think it was around -63db. But, I wanted to get it down some more so that any outside noise wouldn't make such a big impact on the sound.
Now as you can see the walls probably don't block enough noise. I decided to try so oriented strand board. to make the walls have more mass and hopefully block out some noise. I started to create some walls that will fit like puzzle pieces together.
The next step will be to add the insulation and moving blankets. Then create the door and see how soundproof. The booth will be. I need to buy some more insulation and a few more 2x4's to put on tops and bottoms. I left 4 inches on the top so that when I build the ceiling it will fit right in ... like a puzzle. Part 2 coming soon......