The Doppler Effect

The technical definition for the Doppler Effect: " The Doppler effect is when sound waves are either compressed or elongated by an object moving toward or away from us. The waves get compressed on approach just as a train whistle seems to be a higher pitch as it comes toward you." Christian Doppler was the first person to study such an effect, especially in relation to sound waves. One example of this is by understanding the pitch of a noise or sound. The more frequent the sound wave is, the higher the pitch is. The Doppler Effect can also be described as some sort of illusion, because how the sound waves hit our eardrums depends on how close we are to the sound. So, for example, when an ambulance car passes and has an extremely loud siren, when the siren is closest to us, then the sound will be the most high pitched because the frequency is larger--so that is the Doppler Effect.
Here is a video on it! :-)) Enjoy!
http://www.youtube.com/watch?v=Kg9F5pN5tlI