Question

what is echo?.??
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Answer 1

Answer:

a sound that is repeated as it is sent back off a surface such as the wall of a tunnel

Answer 2

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What is echo ?

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A repeated sound that is caused by the reflection of sound waves from a surface. The sound is heard more than once because of the time difference between the initial production of the sound waves and their return from the reflecting surface.

A wave that carries a signal and is reflected. Echoes of radio signals (carried by electromagnetic waves) are used in radar to detect the location or velocity of distant objects.