# Answer to Question #2876 in Acoustics for Rooky

Question #2876

If a train is moving toward you and at a speed of 50 m/sec and emits a whistle sound of pitch 1500 Hz, what will be the frequency with which you hear the pitch?

Expert's answer

Frequency f0, then an observer stationary relative to the medium detects waves with a frequency f given by

f = v/(v + vs) f

where v

In this case v is the speed of sound ( approximately 343 m/s)

Vs=-50 m/sec

So f=(v/(v+v

f = (343/(343-50))*1500 ≈ 1755.97 Hz

Answer : f ≈ 1755.97 Hz

f = v/(v + vs) f

_{0}where v

_{s}is positive if the source is moving away from the observer, and negative if the source is moving towards the observer.In this case v is the speed of sound ( approximately 343 m/s)

Vs=-50 m/sec

So f=(v/(v+v

_{s})) f_{0}f = (343/(343-50))*1500 ≈ 1755.97 Hz

Answer : f ≈ 1755.97 Hz

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