The Echo Tube
Speak or clap into the tube. A moment later, you hear your sound return as an echo.
The tube is about 38 metres long, so the sound travels roughly 76 metres to the far end and back. At about 343 m/s, that takes around 0.22 seconds.
The delay changes slightly with air temperature, because the speed of sound changes.
Make a short, sharp sound. Can you hear the original sound and its echo separately?
Additional Information
Sound travels at about 343 meters per second in air, so a longer tube creates a longer, more noticeable delay before the echo returns. Your brain only perceives two sounds as a distinct echo, rather than one longer sound, if they’re separated by roughly a tenth of a second or more.
Bats and dolphins use the same reflection principle deliberately, called echolocation, to “see” their surroundings using returning sound instead of light.
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