The persistence of sound in a big hall due to repeated reflection of sound from the walls, ceiling and floor of the hall is called reverberation.
Methods to reduce reverberation in big halls or auditoriums
(i) Panels made of felt or compressed fibre board are put on walls and ceiling to absorb sound.
(ii) Heavy curtains are put on doors and windows.
(iii) Carpets are put on the floor.
(iv) Seats are made of material having sound absorbing properties.