Chapter 12, Problem 10CQ

You are standing several meters from the railroad tracks with a train approaching, sounding its whistle. (a) As the train gets closer and closer, what happens to the loudness of the sound? Why? (b) As the train gets closer and closer, the pitch you hear from the whistle gets lower and lower. Why? (c) Would both observations in parts (a) and (b) hold true if you were standing on the tracks? Why?