An observer rides with a moving sound source directly toward a large vertical wall. The vehicle has a constant speed of 10m/s and the source has a frequency of 150Hz. What beat frequency is heard by the observer as a result of the combination of the direct and reflected sounds?

Answer 1

Received frequency shift (df):
df/f = 2*(v/a) = 2*10/340 = 0.059
df = 150*.059 = 8.8 Hz
Received frequency = 150 + 8.8
= 158.8 Hz
Beat frequency = 158.8 - 150 = 8.8 Hz