Abstract
A balcony overhang is frequently set up in auditoria. The sectional shape of the under-balcony space is one of the most important factors for good acoustics in auditoria. The acoustical properties under the overhang, however, have not been clarified yet and there is so far no generally accepted criteria for acoustical design of the balcony configuration. The object of this study is to make clear the relation between the shape of the balcony and the acoustical properties. As the first step, the strength of direct-sound component including the diffraction waves from the edge of the overhang is theoretically and experimentally examined. A new approximate expression is presented for calculating the direct-sound energy under the balcony on the assumption that the balcony is a thin half-plane. According to this approximation, the direct-sound level can be represented by means of two parameters concerning to the fundamental dimensions of auditorium with a balcony. Numerical computations present a chart showing the relation among the direct-sound level and these parameters. And numerical calculations and model experiments show that the accuracy of this approximation is good.
