Well, for those of us who are making our own rooms
, we actually have a say in how thick our walls and floors are as well as what material we use! Let's choose wisely and take the bigger picture in before making decisions. It's much easier to make it the way you want from the beginning! My advice for a reasonably (minimum) sound-proof wall consisting of your average building material is 12mm plywood+12mm sheet-rock this is one side. (If you have a bigger budget you can go for the fiberglass or cellulose insulation.) Putty the joints and throw wallpaper over it and you have your wall!