Defination- The persistence of sound in a big hall due to repeated reflections from the walls, ceilings and floor of the hall is called reverberation.
Few method to reduce reverberation are:-
1) Panels made of sound absorbing materials are put on walls and ceilings.
2) Carpets are put on floor.
3) Heavy curtains are put on doors and windows.
4) The material having sound-absorbing properties are used to make the seats in a big hall.
Sorry, I know don't know about applications of multiple reflection of sound maybe somebody else can help you for that.