A Boy is walking away from a wall at a speed of 1m/s in a direction at right angles to the wall. As he walks, he blows a whistle steadily. An observer toward whom the boy is walking hearts 4 beats per second. If the speed of sound is 340 m/s, what is the frequency of the whistle? My original approach did not come out anywhere near right, so im just going to ask if this analysis of the situation is right. The boy is walking toward someone blowing a whistle. So there are two doppler effects? The one caused from the boy walking toward an observer and the sound wave reflecting off the wall, so I would calculate two doppler effects and combine them? And how can I change beat frequency to frequency, if thats possible even.