Question

why can you not hear the echo if you stand 10 m away from the wall and shout towards it?

Answer 1

This is because of the minimum distance to hear an echo (which is 17m).

Suppose, speed of sound in air is 340m/s. The minimum time taken by an average human to hear an echo is 0.05s

Since,S = v*t Wherein S is distance, v is speed (or) velocity, t is timeTherefore,S = 340*0.05 S = 17m.