a) The noise wall is 15 m from the nearest tire, and is 7 m tall. An apartment is 8 m beyond the barrier and has a window at a height of 2 m. Assume that the sound frequency is 150 Hz. Calculate the insertion loss of the noise barrier. Given speed of sound in air 343 m/s. a 7 m Lm 2 m 15 8 m b) Calculate the insertion loss if barrier with 3 m in height is used. c) Comment on the efficiency of the barriers in a) and b) in reducing noise?