Question

Why do we not get echo in small rooms

Answer 1

as the minimum distance needed for the course of course is 17.2 M

Answer 2

If there are hard 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 furnishings (carpets, curtains, sofas) most of the sound is absorbed anyway. ... This is because of the lack of echos.

I hope this will help you