# What relations between sound frequencies of a sound wave in motion that gets reflected from the wall occur?

Let's say you're driving forward by car and when you press the horn, the sound is reflected from the building in front of us. If we mark the frequency of the sound sent by $$f_1$$, frequency of the sound received by an observer located in the building by $$f_2$$ and frequency of the reflected sound which is received by the observer in the car by $$f_3$$,

What relations can we show for these frequencies?

• How do we describe such wave behavior? is it an example of double doppler-effect? Should any of the frequencies be equal to each other here? – Undergraduate Wannabe Oct 11 at 14:20