Doppler Effect

Describing the classical Doppler Effect for sound waves. The Doppler Effect is a means through that wave properties (specifically frequencies) are influenced through the movement of a source or listener. If you've ever been waiting at a railroad crossing and listened to the train whistle, you've in all probability noticed that the pitch of the whistle changes as it moves associatively to your position. Same, the pitch of a siren change as it approaches and then passes you on the road.