Question

In a cinema theatre, why do we normally not hear echoes even though the sounds are loud?​

Answer 1

Answer:

An echo is formed as a result of reflection of the original sound which returns to the listener. You might have experienced Echo in an EMPTY ROOM but no echo is produced after the room is occupied. To avoid echo from being  produced the echo has to be absorbed. Echo in a cinema theatre is absorbed by the WALLS of the theatre.

They are not plain. The walls are corrugated or shaped to form tiny holes or empty spaces to ABSORB the ECHO. Modern Theatre's have ABSORBENT materials sticked to the walls of the theatre.