Department of Biomedical Engineering, Tohoku University, Sendai, Japan.
J Voice. 2011 Nov;25(6):e255-63. doi: 10.1016/j.jvoice.2010.11.006. Epub 2011 May 7.
Voice is produced by vibrations of vocal folds that consist of multiple layers. The portion of the vocal fold tissue that vibrates varies depending primarily on laryngeal muscle activity. The effective depth of tissue vibration should significantly influence the vibrational behavior of the tissue and resulting voice quality. However, thus far, the effect of the activation of individual muscles on the effective depth is not well understood. In this study, a three-dimensional finite element analysis is performed to investigate the effect of the activation of two major laryngeal muscles, the cricothyroid (CT) and thyroarytenoid (TA) muscles, on vocal fold morphology and stress distribution in the tissue. Because structures that bear less stress can easily be deformed and involved in vibration, information on the morphology and stress distribution may provide a useful estimate of the effective depth. The results of the analyses indicate that the two muscles perform distinct roles, which allow cooperative control of the morphology and stress. When the CT muscle is activated, the tip region of the vocal folds becomes thinner and curves upward, resulting in the elevation of the stress magnitude all over the tissue to a certain degree that depends on the stiffness of each layer. On the other hand, the TA muscle acts to suppress the morphological change and controls the stress magnitude in a position-dependent manner. Thus, the present analyses demonstrate quantitative relationships between the two muscles in their cooperative regulation of vocal fold morphology and stress.
声音是由声带的振动产生的，声带由多层组成。声带组织的振动部分主要取决于喉肌的活动。组织振动的有效深度应该会显著影响组织的振动行为和产生的音质。然而，到目前为止，对于单个肌肉的激活对有效深度的影响还不是很清楚。在这项研究中，进行了一个三维有限元分析，以研究两个主要的喉肌，环甲肌（CT）和杓状软骨肌（TA）的激活对声带形态和组织内应力分布的影响。因为承载较小应力的结构容易变形并参与振动，所以形态和应力分布的信息可能提供有效深度的有用估计。分析结果表明，这两块肌肉发挥着不同的作用，从而可以对形态和应力进行协同控制。当 CT 肌肉被激活时，声带的尖端区域变得更薄并向上弯曲，导致整个组织的应力幅值在一定程度上升高，这取决于每个层的刚度。另一方面，TA 肌肉的作用是抑制形态变化，并以位置依赖的方式控制应力幅值。因此，目前的分析表明，这两块肌肉在协同调节声带形态和应力方面存在定量关系。
