ABSTRACT
The fundamental purpose of a paging, announcement, voice alarm, or speech reinforcement system is to deliver intelligible speech to the listener. A surprising number of systems, however, fail to achieve this basic goal. There can be many reasons for this, ranging from inadequate signal-to-noise ratio to poor room acoustics or inappropriate choice or location of the loudspeaker. It is the job of the sound system designer to be aware of these factors and take them into account when designing a sound system and selecting devices to provide the degree of intelligibility required. In order to do this, however, an understanding of the basic factors that affect speech intelligibility and the way we hear speech is required. This chapter therefore begins by taking a look at the nature of the speech signal and how we hear it before discussing design strategies and ways of optimizing system design and performance. Current methods of assessing and measuring intelligibility are then also discussed together with comments on their practical limitations.
