Why does a police siren change its note as it races past you?
The ambulance, police car, or ice-cream truck that races past you on the street, the "EEEE...ooohh" you hear every time one zooms by. Also a passing motorbike or race car.
Talk about it
- Next time a siren passes, guess together whether the note will go up or down right as it goes by.
- Talk about how the siren itself never changes — only its motion does. Why does that fool our ears?
- Name three things that make this 'EEEE...ooohh' sound: ambulance, race car, what else?