>>410015251
Buy door seal and a door sweep and seal your door.
Make sure there are no holes in your walls. Stack as much furniture as you can against walls adjacent to places where people can hear you on the other side.
Run an air conditioner or anything else that can generate white noise while you're ERPing.

You can't soundproof your room, that's impossible, but you CAN greatly reduce the leakage this way and make it hard for anyone to know what's going on in your room without having to stand right next to your door and eavesdrop, unless you're really loud or high pitched.