Echo (acoustics)

Whales echolocation organs produce echoes and receive sounds
In acoustics, echo is when sound comes back. The word echo come from Greek word ἠχώ (ēchō) from (ēchos), "sound".
In nature echos happen in empty spaces, woods or mountains.
Echo (acoustics) Media
Echolocation organs of a toothed whale, which produce echoes and receive sounds. Arrows illustrate the outgoing and incoming path of sound.