Question

what should be the minimum distance between source of sound and reflecting surface to hear the same sound again and explain why it is required​

Answer 1

Answer:

Since sound has to travel an equal distance in going up to the reflecting surface and in coming back from the reflecting surface, therefore it must travel nearly 33/2 = 16.5 m either way. Thus, to hear the echo clearly in air, the reflecting surface should be at a minimum distance of 16.5 m from the source of sound.