Doppler Effect

Resting sound source Frequency fs V=340m/s Frequency fo source at rest observer at rest

Sound source moving toward observer Observer hears increased pitch (shorter wave length) Frequency fo Frequency fs source observer at rest

Sound source moving away from observer Observer hears decreased pitch (longer wave length) Frequency fo Frequency fs observer at rest source

Frequency heard by observer Source moving toward observer. Perceived wavelength: With Observer:

Observed frequency Source toward observer: Source away from observer: Increased frequency Source away from observer: Decreased frequency