Tokuda Isao T, Shimamura Ryo
Graduate School of Science and Engineering, Ritsumeikan University, Noji-higashi, Kusatsu, Shiga 525-8577, Japan.
J Acoust Soc Am. 2017 Aug;142(2):482. doi: 10.1121/1.4996105.
As an alternative factor to produce asymmetry between left and right vocal folds, the present study focuses on level difference, which is defined as the distance between the upper surfaces of the bilateral vocal folds in the inferior-superior direction. Physical models of the vocal folds were utilized to study the effect of the level difference on the phonation threshold pressure. A vocal tract model was also attached to the vocal fold model. For two types of different models, experiments revealed that the phonation threshold pressure tended to increase as the level difference was extended. Based upon a small amplitude approximation of the vocal fold oscillations, a theoretical formula was derived for the phonation threshold pressure. This theory agrees with the experiments, especially when the phase difference between the left and right vocal folds is not extensive. Furthermore, an asymmetric two-mass model was simulated with a level difference to validate the experiments as well as the theory. The primary conclusion is that the level difference has a potential effect on voice production especially for patients with an extended level of vertical difference in the vocal folds, which might be taken into account for the diagnosis of voice disorders.
作为在左右声带之间产生不对称的一个替代因素，本研究聚焦于高度差，其定义为双侧声带在上下方向上表面之间的距离。利用声带的物理模型来研究高度差对发声阈压力的影响。还在声带模型上连接了一个声道模型。对于两种不同类型的模型，实验表明发声阈压力倾向于随着高度差的增大而增加。基于声带振动的小振幅近似，推导了发声阈压力的理论公式。该理论与实验结果相符，特别是当左右声带之间的相位差不大时。此外，模拟了具有高度差的非对称双质量模型，以验证实验和理论。主要结论是高度差对发声有潜在影响，特别是对于声带垂直高度差增大的患者，这在语音障碍的诊断中可能需要考虑。
