Question

A fire engine is being driven away from you at a speed of 15.4 m/s. One of the notes in its siren sequence has a fundamental frequency of 244 Hz. If the speed of sound is 338 m/s, the fundamental frequency of that particular note will seem to you to be ___Hz. 

Answer 1

Given:

$v_s=15.4\:\rm m/s$

$f_0=244\:\rm Hz$

$u=338\:\rm m/s$

$$f=f_0\frac{u}{u+v_s}=244*\frac{338}{338+15.4}=214\:\rm Hz$$