Doppler's effect,,?

The Doppler Effect has to do with sound waves and moving objects. Imagine yourself standing next to a racetrack with the cars zipping by. As the cars come towards you, the pitch of the sound of their engines will be different than when they are going away from you. This is because when the cars are approaching the sound waves (which travel faster than the car and reach you sooner than the vehicle does) are actually being compressed. The circle diagram I think you might be referring to represents how the waves are being squashed by a moving object. a href="http://www.btinternet.com/~j.doyle/SR/Sr6/sr6.htm" rel="nofollow"http://www.btinternet.com/~j.doyle/SR/Sr…/a has another diagram that might help you understand the process better.