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You are building a recording studio, and want to have a high level of sound isolation between the live room and the control room. This wall will be 3 m wide and 2.5 m tall. You decide on a construction that will have a TL of 60 at 1000 Hz. However, you need to install a window in this wall, and the best window you can afford has a TL of 45 at 1000 Hz. If the window is to be 1.5 m wide and .75 m high, what will the composite TL of the wall be? For the studio above, what would the NR of the wall be if the total absorption in the receiving room is 15 metric sabins?