Soundproofing a room for a musician roommate
Set practice hours and volume limits with the household. Use headphones, electronic instruments, practice pads, mutes, rugs, door seals, and isolation pads to reduce ordinary noise and vibration. Put speakers away from shared walls and floors when possible.
Do not make structural changes without permission. Foam panels reduce echo inside a room but do little to stop bass or drums traveling through a building.
For loud practice, use a rehearsal room or studio. Good neighbor relations are the most effective acoustic treatment.