オーディトリウムのバルコニー形態と初期反射音特性

抄録

The purpose of this study is to make clear the relation between the shape of balcony and acoustical properties under overhangs, and to derive a design criterion for balcony configuration in auditoria. Impulse responses are calculated in models of auditoria by means of computer simulation based on geometrical acoustics when the depth and the height of balcony-opening are varied. The evident effects of overhang can not be found in common acoustical quantities (.SKL, C_<80>, Ts and LE). This means that another index is required for evaluating the lack of auditory envelopment which is often perceived under balcony. Then the relation between the directional characteristics of early reflections and balcony configuration are examined. The result shows that the ratio of vertical energy component to total reflection energy ER_V is extremely reduced under balcony in comparison with that in main orchestra and it is closely related to balcony index of d/h through a regression expression, where d and h are geometrically defined by the positions of sound source, receiving point and balcony edge. Applying the difference limen of ER_V to this relation, it is found that the maximum limit of d/h, within which the degree of auditory envelopment under overhangs is equivalent to that in main seats, lies between 0.7 and 1.3.