Question

where and why are sound absorbing materials used

Answer 1

sound absorbing materials are used in large halls to avoid reverberation. reverberation causes disturbance to the audience as the same sound is Hearn multiple times

Answer 2

Sound absorbing materials are used in Halls to avoid the repeatation of sound again again.
They are mainly a type of fine smooth cloth which does not allow the sound to get reflect.

hope it helps u. . . .