How do we

hear?

Doppler Effect

Doppler Effect• Due to moving sound source• closer to source = greater frequency• farther from source = lesser frequency• as sound moves towards listener the

sound can be a high pitched whine• as sound moves away from listener the

sound can be a drumming sound

Uses of the Doppler Effect• Doppler radar

– police use it to determine speed of car– the frequency of the reflected (echo)

sound wave gives you the speed– weather forecasters can use it to

determine how fast a storm front is moving

– determine the speed of stars relative to Earth

Breaking the sound barrier!Why can’t

I hear anything?

ULTRASOUND!