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Frequency of a Siren

A siren is mounted on a tower and emits a sound whose frequency is 2140 Hz. A person is driving a car awayf rom the tower at 27 m/s. The sound reaches the person by 2 paths: the sound reflected from a buliding in the front of the car and the sound coming directly from the siren. The speed of sound is 343 m/s. What frequency does the person hear for the a) reflected and b) direct sounds.

Solution Preview

When the observer is moving towards/ away from the sound the frequency of the sound that he hears is different from the emitted frequency (Doppler effect)

The equation is
f= fo (1+ speed of observer/ speed of sound)
when the observer is moving towards ...

Solution Summary

The solution calculates frequency for the a) reflected and b) direct sounds.