ASA 125th Meeting Ottawa 1993 May

2aAA7. Spatial information measurements for investigating specular and diffuse sound fields in enclosures.

A. Abdou

R. W. Guy

Ctr. for Building Studies CBS), Concordia Univ., Montreal, PQ H3G 1M8, Canada

Attempts to predict the sound quality in large rooms can be made at the design stage using scale or computer simulation models but they are usually based on the assumption that the sound field is diffuse. Quality is said to be measured in existing rooms by known room-acoustic indicators but most of them have been developed without regard to direction sensing. Measurements in existing halls show that the sound field is far from diffuse. Specular and diffuse surface reflections not only vary from one room to another but also from seat to seat in the same room. To quantify this phenomena, both spatial and temporal diffuseness has to be investigated. Measuring the directional characteristics of sound in existing halls provides the prospect of quantifying such distribution. This work describes the development of a PC-based system to measure the spatial information of sound fields in large rooms. The system utilizes sound intensity measurement from three microphone pairs arranged in Cartesian coordinates or one pair in three successive orientations to calculate intensity vectors. The sound field can then be visualized on an energy directional basis versus arrival time and hence analyzed in greater detail than hitherto possible. The potential for quantifying spatial specular and diffuse sound fields will be discussed and example results presented. Such results may lead to new acoustic indices with respect to direction dictated quality. [Work supported by NSERC, Canada, Individual Operating Grant OGPIN 013.]