ABSTRACT
This chapter opens with an overview of the different requirements for sound reinforcement systems, such as the minimum sound level required, acceptable sound level distribution, clarity of reproduction, naturalness of transmission, and finally freedom from positive acoustic feedback. Sound level calculations outdoors as well as indoors are followed by layout issues starting with information systems. In addition to simple calculations for flat rooms (use of ceiling loudspeakers) and high ceiling areas, installations in exhibition halls, in the open air and traffic facilities are explained. Furthermore, information systems in sound-reflecting halls such as churches are mentioned. This is followed by the calculation of the achievable acoustic gain of a simple sound reinforcement system. The most important determining factors are mentioned, including the geometrical arrangement of source and listener and of the microphone and the loudspeaker. A diagram and corresponding calculations are introduced that facilitate the optimization of the achievable acoustic gain. For more complex systems, computer simulation is required to calculate the gain to avoid acoustic feedback. Delay-related problems, especially in multichannel systems, will be explained in the next section. With correct arrangement of the loudspeakers being used, naturalness and correct source localization are ensured. Modern sound reinforcement techniques such as source orientation and immersive environments are explained. Finally, sound reinforcement issues in multi-purpose halls are outlined. A distinction is made between dry and reverberant halls. At the end of this chapter, the use of assistive listening systems using induction loops, infrared transmission and FM transmission is presented.
