马铁菊头蝠声道声学特性的数值分析

采用有限元数值计算得到了马铁菊头蝠声道内部的声场分布,给出了马铁菊头蝠声道内几种特殊的腔体结构在蝙蝠发声过程中的作用。通过微型CT扫描并经过三维重构得到了马铁菊头蝠声道的三维立体模型用于有限元数值计算,通过在声门处放置单位声源计算得到了整个声道内部以及鼻孔周围的声压分布。结果表明,马铁菊头蝠声道包含了鼻腔结构后声波在声门上方的声压幅度明显大于不含鼻腔结构的情况,从传输曲线来看,声门上方鼻腔的存在使得系统对声波传输在二次谐波频率处呈现低阻抗效果,同时鼻腔的改变还可影响二次谐波的位置。而声门下方的气管空腔主要影响声波的背向转播,声门下方的气管空腔的存在可明显降低蝙蝠发声时声场在声道声门下方的声压幅度,同时抑制声音背向传播时二次谐波成分的强度。

Numerical analysis of the acoustic role of vocal tract in the horseshoe bat

The sound field distribution and effects for sound pressure in vocal tract of the horseshoe bat, Rhinolophus ferrumequinum, have been obtained using FEM technique. The models of vocal tracts used for FEM calculation are constructed by tomography scanning. These models are used to set up finite element model for calculating the sound field distribution by loading the unit sound source in glottis. By change the frequency of the unit sound source the frequency response was figured out and the acoustic role of vocal tract chambers was examined by obtaining the transfer function and sound pressure distribution before and after filling the chambers using voxels. Sound pressures in the trachea and nostrils are recorded and some analysis of the acoustics of subglottal and vocal tract was made to find the function of the construction in vocal tract and subglottal parts. The results show nasal chambers can effectively improve the Q (quality factor) value near the second harmonic, and alternate the sound distribution in the supraglottal part. whereas the tracheal chambers can reduce the amplitude of the sound pressure in the subglottal part, their function is like a band block filter which can block the second harmonic component of the back propagation sound under the glottis.