Hey! If you're looking to control the acoustics in the room try acoustic foam. Acoustic foam is great for improving recorded sound quality and to an extent soundproofing a room. If you truly want to soundproof a room, as in isolating all noise, that's going to be an expensive project.
There's lots of different acoustic foam types. All are used to control different frequencies. high to medium frequency soundwaves you'll want something like pyramid shaped tiles I believe and the thicker the better for low soundwaves.
Hope that helps :) Let me know if you need anymore help.