Question

Mention the conditions which are required for the echo to be heard?

Answer 1

1. An echo can be defined as a reflection of sound that arrives at the listener with a delay after the direct sound.
2. The necessary conditions for hearing an echo are:
   a) The distance between the sound source and the place where it is reflected from must not be less than $\text{17m}$.
   b) The period between hearing the original sound and its echo should not be less than $0.1$ of a second.