ABSTRACT
This chapter deals with sound propagation in a medium which was unbounded in every direction. In contrast to this simple situation, room acoustics is concerned with sound propagating in enclosures where the sound-conducting medium is bounded on all sides by walls, ceiling and floor. The chapter encounters the concepts of wall impedance and absorption coefficient, which are of special importance in room acoustics. Any free edge of a reflecting wall or panel scatters some sound energy in all directions. The same happens when a sound wave hits any other obstacle of limited extent, such as a pillar or a listener’s head, or when it arrives at a basically plane wall which has an irregular surface. The acoustical properties of a wall surface—as far as they are of interest in room acoustics—are completely described by the reflection factor for all angles of incidence and for all frequencies.
