A study on acoustical design method considering the effect of directional characteristics of sound source

本研究的目的是明确声源在礼堂舞台上的基本特征，即声源的指向性模式、主轴方向和声源位置对声学性能和房间形状评价的影响，而这些通常只有在全向声源的情况下才能进行估计。首先，采用基于几何声学的计算机模拟方法，计算了两种乐器声源方向分布变化时的脉冲响应。研究了声源的方向性与脉冲响应得到的基本声学指标（C_<80>、EDT和LE）之间的关系。结果表明，在C_<80>范围内，方向性的锐化使噪声增大2.0 ~ 4.0 dB，而在EDT范围内则减小10 ~ 30%以上。其次，通过计算礼堂变平面模型的声学指标，考察了方向与最佳房间形状之间的关系。结果表明，声源的方向性对最佳房间形状的确定有很大影响，在音乐厅声学设计中，必须认真考虑弦乐等乐器的方向性特征。

The purpose of this study is to make clear the effect of the fundamental characteristics of sound source on stage of auditoria, that is, directivity pattern, orientation of main axis and location of source, on the acoustical properties and evaluation of room shape, although they are ordinarily estimated only with omni-directional source. First, impulse responses are calculated in two models of auditoria by means of computer simulation based on geometrical acoustics when the directional distribution of sound source modeled on musical instruments are varied. The relations between the directionality of sound source and basic acoustical indices (C_<80>, EDT and LE) which are obtained from impulse responses, are examined. The result shows that the sharpness of directionality brings about the increase of 2.0-4.0 dB in C_<80> and the decrease of above 10-30% in EDT.Secondly, the relation between the directionality and optimal room shape is examined by calculating the acoustical indices in variable plan models of auditoria. The result shows that the directionality of sound source affects strongly the proper determination of optimal room shape and a careful consideration on the directional characteristics of musical instruments like strings is necessary in acoustic design of concert halls.