Studio Room Treatments
Studio room treatment is not an exacting science since not all rooms are created equal. Rooms for a mastering studio can come in all different shapes, sizes, and angles. Preferably a square or a bit rectangular room shape is best.
What can influence how you may use room treatments is based off the make of the wall. Walls can be hollow or solid with different types of covering such as plaster, wood, stone, etc. How the sound is going to bounce off of these different types of wall surfaces has to be considered for the placement of wall sound proofing treatments. Like it was mentioned before the acoustics of a room for mastering need to be tamed appropriately for proper listening in mastering sessions.
A couple ways the walls are treated is with a stucco foam, actual carpet on walls which has a very good noise reduction effect. For example if you ever experienced moving to a new empty house an you notice all the echo & reverbification of the room when you walk or talk. Why? because there is nothing in the room containing the sound. It is free to vibrate all over the place making for a pretty noisy room. Even outdoor sounds will be louder with open windows in a empty untreated room.
So now you can understand the purpose & need for a room to be treated for the purpose of mastering song audio. No mastering engineer would ever want to attempt to master a song or a project of a multitude of songs in a room that has not been prepared with all the necessary room treatments. let