Department of Otolaryngology-Head and Neck Surgery, University of Cincinnati, 231 Albert Sabin Way, Cincinnati, Ohio 45267, USA.
J Acoust Soc Am. 2019 May;145(5):3137. doi: 10.1121/1.5108889.
Dysfunction of the velopharyngeal valve in the human airway causes speech disorders because there is no separation between the oral and nasal cavities during normal oral speech. The speech literature hypothesizes that undesired sound is formed by turbulent flow in the nasal cavity in cases of small velopharyngeal openings. The aim is to determine the flow behavior and the sound-generating mechanism in the vocal tract using computational fluid dynamics in two patient-specific models with small and large velopharyngeal openings and contrast it with cases of complete velopharyngeal closure. The geometry for the models was reconstructed from computed tomography scans that were taken while the patients were sustaining a sibilant sound. The results for the turbulence are correlated with the broadband acoustic models of Proudman and Curle. The models show that turbulence in the vocal tract increases downstream of a constriction and that sound may be generated from it. Furthermore, most of the sound due to turbulence in the nasal cavity is governed by a dipole source where turbulence interacts with the nasal cavity walls. The generated sound power by turbulence itself in the nasal cavity (the quadrupole source) is two orders of magnitude less than the dipole source.
人类气道中的软腭咽瓣功能障碍会导致语音障碍，因为在正常的口腔语音中，口腔和鼻腔之间没有分离。语音文献假设，在软腭开口较小的情况下，鼻腔中的湍流会形成不希望的声音。目的是使用计算流体动力学在两个具有较小和较大软腭开口的特定于患者的模型中确定流动物理特性和发声机制，并将其与完全软腭闭合的情况进行对比。模型的几何形状是根据患者发出摩擦音时拍摄的计算机断层扫描重建的。将湍流结果与 Proudman 和 Curle 的宽带声学模型相关联。模型表明，湍流会在收缩下游增加，并且声音可能由此产生。此外，鼻腔中湍流产生的大部分声音受偶极子声源控制，其中湍流与鼻腔壁相互作用。鼻腔中湍流本身产生的声音功率（四极子声源）比偶极子声源小两个数量级。
