Early sound distribution in auditorium

The importance of early sound, i.e., the direct sound and the first reflections, has long been recognized in auditorium design, but the distributions of early sound in auditorium received less investigation in the past. As we know, the early sound level in the audience area varies not only with the source/receiver distance and room constant, but also related with the room geometry, the absorption arrangement and the location of the source and receiver. The early reflections are of discrete components, so it can not be predicted by the diffused field theory. This paper presents the results of measurement in four halls showing the attenuation rates of early sound level with the source/receiver distance are often much larger than the theoretical predictions. Therefore, they may give overestimated results in acoustical design.