Measurement of spatial information in sound fields by a closely located four-point microphone method

Abstract

When an estimation is made of the sound field in a room, it is important to grasp spatial information, especially for the early reverberation periods. Here, a way to grasp spatial information of sound fields from impulse responses measured at four closely located points, the origin, and three points the same distance (3∼5 cm) from the origin on the rectangular coordinate axes will be discussed. From these four impulse responses the position of virtual image sources are calculated by the correlation and/or intensity technique. Concert halls in Europe, the United States, and Japan and some scale models are measured by this method. The three-dimensional distribution of virtual image sources, directivity patterns, and impulse responses from several directions are shown. Calculation of signals from special directions by convolving these impulse responses with dry music to estimate the sound fields with ears or to help the acoustic design, and the introduction of the Wignet distribution are also discussed.