Doppler Effect

When a car or Ambulance drives by, you'll notice that the pitch changes. As the car is closest to you the pitch will be highest. why? This is because the frequency of the mechanical, longitudinal sound wave is at its highest point when closest to you. This also means that it has the most amount of Hertz when its closest.

If you are asked a question about amount of Hertz when a car moving at constant speed is a certain distance from you, then closest to you, with the given being the amount of Hertz at the further distance, then what is the amount of hertz when it is closest to you? The answer is greater than the amount of hertz of the distance further away.