(a) Geometrical construction used to determine the plane of a reflector in (c) and (d); (b) paths of direct sound, and several reflected sound waves in a 19th-century concert hall with traditional horizontal floor and ceiling and parallel side walls (the 
Extract
(a) Geometrical construction used to determine the plane of a reflector in (c) and (d); (b) paths of direct sound, and several reflected sound waves in a 19th-century concert hall with traditional horizontal floor and ceiling and parallel side walls (the diagram illustrates the different types of reflection which aid listening in a concert hall; after Beranek, 1962); (c) plan of the seating (shaded) and stage, showing the complexity of the calculations necessary to determine the wall reflectors of a small auditorium; (d) shape of the floor and ceiling of same, showing the calculation for the ceiling reflectors (after Bagenal and Wood, 1931)...
