Doppler’s Effect

 

Doppler’s Effect

If either the source of sound or the observer is moving, then there will be a change in frequency and wavelength for the observer. The frequency will be higher when the observer moves towards the source, and it decreases when the observer moves away from the source.

Example: If one is standing on a street corner and an ambulance approaches with its siren blaring, the sound of the siren steadily gains in pitch as it comes closer and then, as it passes, the pitch suddenly lowers.