When a sound wave emitted in an enclosed environment meets a wall, a part of its energy passes through it, a part is absorbed by it and a part is reflected in the environment. If the amount of reflecting surface of an environment is high, it will be so reverberating that it becomes annoying to listen to any sound. Even if there is little furniture in a room, the reverberation effect is very strong. You can notice it in hotel corridors or waiting rooms.
In crowded places such as restaurants, pubs and schools, people talking to each other are forced to rise their voice volume to overcome the background noise. In technical environments it is necessary that the acoustic quality is above average, for example in meeting rooms, conference rooms, congress centres, theaters etc.. It often happens that people invest in a building structure, but the investment is ruined by the poor acoustic design of the whole building or the single room.