How Far Away Is the Echo?

Name: How Far Away Is the Echo?
Uploaded: 2026-11-08T12:48:16+00:00
Duration: 36 s
Description: Hear a pulse and its echo 0.40 seconds later, then work out how far the sound travelled.

Hear a pulse and its echo 0.40 seconds later, then work out how far the sound travelled.

How far does the sound travel?

At 20 °C, sound travels about 343 metres per second through air. In 0.40 seconds it travels about 137.2 metres. The echo covers the trip out and back, so the reflecting surface would be about 68.6 metres away.

The pulses in this video use simulated delays. At the same sound speed, the 0.20-second example would put the reflector about 34.3 metres away.

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