What Causes the ‘Doppler Effect’ and Why Do We Notice It?

The Doppler Effect is like when you're on a bike and you hear a bell. When the person ringing the bell moves toward you, the sound seems higher, it's like they’re shouting louder. But when they move away from you, the sound gets lower, like they’re whispering. It all happens because of how waves work.

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Examples

A train whistling as it passes by a station, you hear a higher pitch as it approaches and then a lower one as it moves away.
You’re riding your bike, and a friend on a scooter rings their bell. As they come toward you, the sound is sharp and clear; when they move past you, it sounds muffled.
A car honking its horn as it zooms by, the sound changes dramatically from high to low in just seconds.

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Categories: Physics · Doppler Effect,Sound Waves,Wave Motion