Limitations of current sound system intelligibility performance measurement techniques and metrics

Abstract

The current and increasing trend to employ sound systems for emergency warning and evacuation purposes has led to an increased need to verify and assess the intelligibility performance of such systems. Applications range from passenger cabin PA systems in aircraft through to paging and emergency evacuation systems in industrial complexes, train stations, public buildings, and stadiums. Although a number of methods are available, these have either been borrowed from the fields of architectural and auditorium acoustics or one-dimensional communication networks. The paper shows that such approaches exhibit a number of fundamental inherent limitations that can lead to significantly reduced accuracy when assessing typical sound system performance. Although important factors such as background noise and reverberation can be accounted for, it is shown that the typical, nonlinear amplitude and frequency response characteristics of many systems are not adequately addressed. Furthermore, common temporal distortions such as discrete specular reflections or later arriving echoes are also shown to result in inaccurate assessments. The need for a simple, easy to use, and yet robust measurement technique is highlighted.