Awesome! Nice to see building materials put to good use rather than end up in a dumpster. Hers a pic of what I did in my space for sound treatments. I used the safe and sound insulation that djnagle mentioned. They’re just 2x4 frames with the battens put vertically in between them. Build the frames about an inch smaller on each side and they stay in place fine. Covered them with a roll of cheap burlap. Made a huge difference in the sound, and the room is all brick!