A car sounding its horn (rated by the manufacturer at 600 Hz) is moving at 20 m/s toward the eat. A stationary observer is standing due east of the oncoming car.

Question

A car sounding its horn (rated by the manufacturer at 600 Hz) is moving at 20 m/s toward the eat. A stationary observer is standing due east of the oncoming car. 
a) What frequency will he hear assuming that the speed of sound is 343 m/s?
b) What if the observer is standing due west of the car as it drives away?

Henry · Accepted Answer

a. Fr = ((V+Vr)/(V-Vs))*Fs.
Fr=((343+0)/(343-20)) * 600Hz.=637.15 Hz
= Freq. heard by the receiver(person).

b. The Fre. heard by the observer would be less than 600 Hz.

Fr = ((343-0)/(343+20)) * 600 = 566.94 Hz.