Question

what is echo ? And what is loudness ??

Answer 1

Echo is the reflection of sound from any obstacle . For echo minimum distance should be 17 m .

Loundness is nothing special but simply it is related throught amplitude .
eg. Lion has more Loundness than bird

Answer 2

echo is vibration of sound mainly happen in caves as rock r hard loudness is how loud or soft voice is 17 m distance is required to happen echo