镜面反射界面条件下扁平空间中的声能衰减

扁平空间是水平方向尺寸远大于高度的体型不规整空间,经典扩散声场理论不适用。本文运用声像法分析了界面作镜面反射条件下的扁平空间中的声能衰减特性,以及各主要因素的影响。模拟结果表明:近场处的声能衰减曲线呈明显的下凹状,混响时间大于早期衰变时间;随着接收点到声源距离的增大,混响时间和早期衰变时间均迅速地到达各自的最大值,然后缓慢地下降;增加底面和顶面的吸声系数差异可以有效地降低远场处的混响时间。

SOUND DECAY IN FLAT ENCLOSURES WITH GEOMETRICALLY REFLECTING BOUNDARIES

The subject of this paper is flat enclosures,where the height is small compared to dimensions in the horizontal directions,to treat it on the basis of diffuse-field theory would yield misleading results because we cannot expect diffuse sound fields in such highly disproportionate spaces.Thus,theoretical formulae for predicting the temporal distribution of sound energy in infinitely extended flat enclosures with geometrically reflecting boundaries were derived by applying the image source model,where the variations in reverberation along the length and the form of decay curves were considered.Computations with these formulae show that in infinitely flat enclosures: with the increase of source-receiver distance,the reverberation time increases sharply to a maximum and then decreases slightly;the decay curves are convex,especially in the near field.