Hysteresis of aeroacoustic sound generation in the articulation of [s]
Hysteresis of aeroacoustic sound generation in the articulation of [s]
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DOI：
10.1063/5.0020312
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发表时间：
2020-10-01
影响因子：
4.6
通讯作者：
Iida, Akiyoshi
中科院分区：
文献类型：
--
作者：
Yoshinaga, Tsukasa;Nozaki, Kazunori;Iida, Akiyoshi
众所周知，摩擦辅音(如[S])是通过口腔内的湍急喷流发音的。本文采用简化的声道模型，通过可压缩流动的大涡模拟，研究了舌头运动对S发声过程中气动发声的影响。简化模型的壁面采用体积惩罚法作为浸没边界方法，舌面几何形状从/u/到/S/的位置以40 mm/S、60 mm/S和80 mm/S的舌速上升和下降，并将远场采样点的模拟声压与以往的实验测量结果进行了比较，模拟声学特性与实验结果吻合较好。总的声幅随着舌头的上升和下降而增加和减少，这些幅度的转变对于不同的舌速几乎是相同的。同时，我们发现舌上升和舌下降之间的整体声幅存在滞后效应。这种滞后性是由于舌下降时上、下牙附近的速度波动和涡流较大所引起的，结果表明，这种流动差异是由于湍流结构的惯性和声道狭窄处的气动压力造成的。这项研究表明，这些现象导致了[S]发音的延迟。
A fricative consonant (e.g., [s]) is known to be pronounced by a turbulent jet flow inside the oral cavity. In this study, the effects of tongue motion on the aeroacoustic sound generation during the articulation of [s] were investigated through the large eddy simulation of compressible flow using a simplified vocal tract model. The walls of the simplified model were expressed using a volume penalization approach as an immersed boundary method, and the tongue geometry was ascended and descended from the position of /u/ to /s/ with tongue speeds of 40 mm/s, 60 mm/s, and 80 mm/s. The simulated acoustic pressure at a far-field sampling point was compared with previous experimental measurements, and the acoustic characteristics of the simulated sound reasonably agreed with those of the experiment. The overall acoustic amplitudes increased and decreased in accordance with tongue ascent and descent, and these transitions in amplitudes were almost the same for the different tongue speeds. Meanwhile, we found a hysteresis effect on the overall acoustic amplitudes between tongue ascent and tongue descent. This hysteresis was caused by the larger velocity fluctuations and vortices near the upper and lower teeth during tongue descent, and the results indicated that these flow differences occurred owing to the inertia of the turbulent flow structures and the aerodynamic pressures over the constriction of the vocal tract. This study suggests that these phenomena cause a delay in the sound generation of [s].