1. The TL of 10 mm thick sheet of plywood at 1000 Hz is 34 dB. Based on the Mass Law, what is the expected TL: a. At 63 Hz? b. At 31 Hz for a 20 mm thick sheet? 2. Two adjacent rehearsal rooms are separated by a 4" thick brick wall (TL250 Hz = 33 dB). The common wall is 10 m high and 10 m long. The total absorption in the receiving room is 200 metric sabins. A guitar playing in one room produces a measured sound pressure level at 250 Hz of 80 dB in that source room. a. What is the NR at 250 Hz? b. What would the level be in the receiving room?