The Science of Sound: Ambulance Edition

[00:00:00]Why does an ambulance's siren change pitch as it zooms past you?

[00:00:05]We all know that an ambulance siren is loud and urgent. Yet, as it approaches, the pitch shifts higher, and then >> [music] >> it drops as it moves away.

[00:00:15]It's called the Doppler effect. Moving objects compress sound waves ahead and stretch them behind.

[00:00:22]Think of it like a Slinky. Push one end and the coils bunch [music] up. Pull and they spread out.

[00:00:28]This wave compression changes the sound's pitch. High as it nears, low as it departs.

[00:00:35]Next time you hear it, remember it's a dance of waves and motion. So, that changing pitch it's sound waves in motion. A symphony of speed.