Question

What is echo? Why don't we get echo in small room

Answer 1

An echo can be heard if the distance between the source and the obstacle is at least 17 m.

In a small room this distance is not met, and hence, we cannot hear an echo.

Answer 2

echo is the repetition of sound wave after striking on a hard surface

I think if there are heart walls there will be an echo of the sound bouncing off the wall but because the sound bouncing is so close to the original it's harder to detect if you have a small room with soft furnishing like carpets curtain sofas at cetera most of the sound is absorbed anyway

hope it will help