The Doppler Effect

The Concept: A Shift in Frequency

The Doppler Effect is the change in frequency of a wave in relation to an observer. As the source moves towards an observer, the sound waves get compressed, leading to a higher perceived frequency (higher pitch). As it moves away, the waves stretch out, leading to a lower perceived frequency (lower pitch).

What to look for

• This simulation shows a "snapshot" of the wavefronts from a moving source.
• The source (speaker) is moving to the right.
• Observe how the wavefronts bunch up in front and spread out behind.
• The analysis panel shows the exact frequencies heard by each observer.