Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.
Department of Speech, Language and Hearing Sciences, Boston University, Boston, MA, 02215, USA.
Biomech Model Mechanobiol. 2023 Feb;22(1):339-356. doi: 10.1007/s10237-022-01652-8. Epub 2022 Nov 12.
Fundamental frequency patterns during phonation onset have received renewed interest due to their promising application in objective classification of normal and pathological voices. However, the associated underlying mechanisms producing the wide array of patterns observed in different phonetic contexts are not yet fully understood. Herein, we employ theoretical and numerical analyses in an effort to elucidate the potential mechanisms driving opposing frequency patterns for initial/isolated vowels versus vowels preceded by voiceless consonants. Utilizing deterministic lumped-mass oscillator models of the vocal folds, we systematically explore the roles of collision and muscle activation in the dynamics of phonation onset. We find that an increasing trend in fundamental frequency, as observed for initial/isolated vowels, arises naturally through a progressive increase in system stiffness as collision intensifies as onset progresses, without the need for time-varying vocal fold tension or changes in aerodynamic loading. In contrast, reduction in cricothyroid muscle activation during onset is required to generate the decrease in fundamental frequency observed for vowels preceded by voiceless consonants. For such phonetic contexts, our analysis shows that the magnitude of reduction in the cricothyroid muscle activation and the activation level of the thyroarytenoid muscle are potential factors underlying observed differences in (relative) fundamental frequency between speakers with healthy and hyperfunctional voices. This work highlights the roles of sometimes competing laryngeal factors in producing the complex array of observed fundamental frequency patterns during phonation onset.
由于在正常和病理嗓音的客观分类中有应用前景，声门起始时的基频模式重新引起了人们的兴趣。然而，在不同语音环境中观察到的广泛的模式所涉及的相关潜在机制尚未完全理解。在此，我们采用理论和数值分析的方法，努力阐明导致初始/孤立元音与无声辅音前的元音呈现相反的基频模式的潜在机制。我们利用声带的确定性集总质量振子模型，系统地研究了碰撞和肌肉激活在声门起始动力学中的作用。我们发现，正如在初始/孤立元音中观察到的那样，基频呈上升趋势，这是由于随着起始的进行，碰撞加剧导致系统刚度逐渐增加，而无需时变声带张力或空气动力学负载的变化。相比之下，需要减少环甲肌在起始时的激活，才能产生无声辅音前元音的基频降低。对于这种语音环境，我们的分析表明，环甲肌的激活减少的幅度以及杓状软骨肌的激活水平是健康和高功能嗓音说话者之间（相对）基频差异的潜在因素。这项工作强调了有时相互竞争的喉部因素在产生声门起始时观察到的复杂基频模式中的作用。
