Question

Why do echoes produced in an empty auditorium usually decrease when it is full of people

Answer 1

Echoes produced in an empty auditorium usually decrease when it's full of people due to the absorption of sound as the  people and their clothes are bad reflectors of sound.

Hope it helps!

Answer 2

Reason for decreases echo, in hall full of people is given below -

•Echo is reflection of sound, heard after 0.1 s and when distance from source is 17 m.

•Now in a room full of people, there are two reasons for decrease in echo -

1. Sound not only reflects from wall, but also from lot of people present there, thus first criteria where distance should be 17 m is not fulfilled.

2. Echo mixes with people's voices or sounds, thus clarity of echo is not maintained.

Hence, echoes decrease in room full of people.