Question

what is an eco?
why we can not hear eco in ordinary surrounding?

Answer 1

echo is the rehearing of sound . it can only heard in mountainy areas because it's has a limited distance that is 17 . 2 m

Answer 2

Eco is the reflection of sound waves .
Eco happens when the sound waves hit an obstacle and travel back.
We normally don't hear echo's because in our surrounding, as nowadays the buildings and most of he infrastructure constructed , even the buses, cars etc, are designed to absorb sound and reflect very negligence amount of them. Even if they would be reflected they wouldn't be heard as there would be some intrupting noises which may prevent