Measurement of spatial information in auditorium by four closely located microphones

Abstract

Quite different impressions are felt in sound fields that have about the same reverberation time and sound pressure level. This kind of difference might come from the difference of spatial information, so it is important to grasp the spatial information in sound fields, especially of the early reflection periods. In this presentation, a way to grasp the spatial information of sound fields from impulse responses measured at four closely located points; the origin and three points of the same distance, 5 cm from the origin on the rectangular coordinate axes, is discussed. From these four impulse responses, the coordinates and powers of virtual image sources are calculated by correlation or intensity technique. Concert halls, opera theaters, and many other sound fields are measured by this technique. This measurement has been introduced not only to actual sound fields, but also to scale models. The distributions of virtual image sources and directivity patterns of auditoria and scale models are shown. These data bases are being used to estimate the sound fields and feed them back to acoustic design of auditoria.