On the Freeway

Once in a while, an ambulance has to come through traffic on the freeway. This was the case for today.

From far away, I can never tell what direction the ambulance is coming from, but as it gets closer, I realize that it's coming from behind me. This is due to the Doppler Effect because as the moving object (the ambulance) is coming to the stationary object (me in the car that has pulled over), the frequency from the siren goes higher. The equation used would be the velocity of the sound's frequency divided by the frequency's velocity minus the velocity of the ambulance. Then all that is multiplied by the actual sound's frequency to get the frequency that I would hear as it approaches. Thus the sound seems more high-pitched and loud when it is coming toward me. After it passes me, the frequency that I hear becomes less.