An ambulance is traveling north at 55.9 m/s, approaching a car that is also traveling north at 28.4 m/s. The ambulance driver hears his siren at a frequency of 983 Hz. The velocity of sound is 343 m/s. At what frequency does the driver of the car hear the ambulance's siren?

915 Hz

Explanation:

The observed frequency from a sound source is given as

f₀ = f [ (v + v₀) / (v+vₛ) ]

where

f₀ = observed frequency of the sound by the observer = ?

f = actual frequency of the sound wave = 983 Hz

v = actual velocity of the sound waves = 343 m/s

vₛ = velocity of the source of the sound waves = 55.9 m/s

v₀ = velocity of the observer = 28.4 m/s

f₀ = 983 [ (343+28.4) / (343+55.9) ]

f₀ = 915.2 Hz = 915 Hz