Question

A train in a station sounds its whistle at a frequency of 512 Hz while moving toward a stationary observer at 4 m/s. A stationary train sounds its 512 Hz whistle at the same time. What is the difference in the frequencies heard, assuming a sound speed of 344 m/s?

Answer 1

$$\Delta f=\frac{344}{344-4}512-512=6.02\ Hz$$