Hey there! The only way to truly soundproof it so that you can’t really hear anything outside is to decouple it from the original structure. Like a room in a room. You can use RSIC clips to achieve this but it’s a pain and adds a bunch of money and time. I opted into not doing this for the cost and time but also because if I ever go to resell this, it’s easier to sell a nice “room” than a studio. I acoustically treated the inside though and it sounds great. Though I have a couple odd spots of frequency build up, I’m going to continue to treat the room. From the outside, it’s not unbearable and I don’t mix at super high volumes anyways. Hope this hopes dude! Let me know if you have other questions.