Observer and a source of sound moving directly toward each other: f ' = f *[v + vo / (v - vs)]

Observer and a source of sound moving directly away from each other: f ' = f *[v - vo / (v + vs)]

Source moving toward observer(stationary): f ' = f *[v / (v - vs)]

Source moving away from observer(stationary): f ' = f *[v / (v + vs)]

A train moving at a speed of 60 m/s sounds its whistle, which has a frequency f = 600 Hz. What is the frequency f ' heard as the train approaches an observer?

f ' = 600 Hz * [ 340 m/s / (340 m/s - 60 m/s)] = 728.6 Hz

What is the frequency heard after the train has passed the observer?

f ' = 600 Hz * [ 340 m/s / (340 m/s + 60 m/s)] = 510 Hz