Using a continuum model based on magnetic resonance imaging of a canine larynx, parametric simulations of the vocal fold vibration during phonation were conducted with the cricothyroid muscle (CT) and the thyroarytenoid muscle (TA) independently activated from zero to full activation. The fundamental frequency (f₀) first increased and then experienced a downward jump as TA activity gradually increased under moderate to high CT activation. Proper orthogonal decomposition analysis revealed that the vocal fold vibrations were dominated by two modes representing a lateral motion and rotational motion, respectively, and the f₀ drop was associated with a switch on the order of the two modes. In another parametric set where only the vocalis was active, f₀ increased monotonically with both TA and CT activity and the mode switch did not occur. The results suggested that the active stress in the TA, which causes large stress differences between the body and cover, is essential for the occurrence of the rotational mode and mode switch. Relatively greater TA activity tends to promote the rotational mode, while relatively greater CT activity tends to promote the lateral mode. The results also suggested that the vibration modes affected f₀ by affecting the contribution of the TA stress to the effective stiffness. The switch in the dominant mode caused the non-monotonic change of f₀.

中文翻译：

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犬喉三维模型中环甲和甲状腺杓肌相互作用引起的声带振动模式变化

使用基于犬喉磁共振成像的连续模型，在环甲肌 (CT) 和甲状腺杓状肌 (TA) 从零激活到完全激活的情况下，对发声过程中的声带振动进行了参数模拟。基频 ( f ₀ ) 首先增加，然后随着 TA 活动在中到高 CT 激活下逐渐增加而出现下降。适当的正交分解分析表明，声带振动分别由代表横向运动和旋转运动的两种模式主导，并且f ₀下降与两种模式顺序的转换有关。在另一个只有人声活跃的参数集中，f ₀随着 TA 和 CT 活动单调增加，并且没有发生模式切换。结果表明，TA 中的主动应力会导致车身和盖子之间出现较大的应力差异，这对于旋转模式和模式切换的发生至关重要。相对较大的 TA 活动倾向于促进旋转模式，而相对较大的 CT 活动倾向于促进横向模式。结果还表明，振动模式通过影响 TA 应力对有效刚度的贡献来影响f ₀。主导模式的切换导致f ₀的非单调变化。