The early reflections in the sound field of an auditorium have important roles in the impulse response and transfer function. The practical calculations are already shown for the first reflections from the boundaries and compared with measured reflections in good agreement. In this paper, the estimation of the multiple reflections between rigid plane panels is treated, based on these. When a panel is small, or the distance between a point source or a receiving point and the panel is large, the multiple reflection of a boundary wave cannot be neglected compared with that of a geometrical wave. Because the first reflection of a rigid plane panel has separate geometrical wave and boundary waves, the multiple reflections between them are obtained by those of each wave. Since a boundary wave is explained as the contribution of lined point sources with directivity on an edge, its multiple reflection is calculated as their geometrical reflection and their boundary waves of a reflecting panel. This calculation method is applied to two rigid plane panels which have a broad angle in between, and two which are in parallel. The calculated results are compared, in the time and frequency domains, with measured values in good agreement.
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