Why are the walls, roof, seats and steps, of a cinema theatre or auditorium covered with special material ?

Explanation

In theatres, auditoria, big halls, etc., due to the reflection of sound from the walls, the floor and the ceiling, the music or the speech rendered becomes uninteresting or unintelligible. To avoid this problem the windows, doors, etc., are covered with thick curtains and the seats and steps are covered with sound absorbing material like carpets.