Triangular body-cover model of the vocal folds with coordinated activation of five intrinsic laryngeal muscles with applications to vocal hyperfunction
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Poor laryngeal muscle coordination that results in abnormal glottal posturing is believed to be a primary etiologic factor in common voice disorders such as non-phonotraumatic vocal hyperfunction. An imbalance in the activity of antagonistic laryngeal muscles is hypothesized to play a key role in the alteration of normal vocal fold biomechanics that results in the dysphonia associated with such disorders. Current low-order models are unsatisfactory to test this hypothesis since they do not capture the co-contraction of antagonist laryngeal muscle pairs. To address this limitation, a scheme for controlling a self-sustained triangular body-cover model with intrinsic muscle control is introduced. The approach builds upon prior efforts and allows for exploring the role of antagonistic muscle pairs in phonation. The proposed scheme is illustrated through the ample agreement with prior studies using finite element models, excised larynges, and clinical studies in sustained and time-varying vocal gestures. Pilot simulations of abnormal scenarios illustrated that poorly regulated and elevated muscle activities result in more abducted prephonatory posturing, which lead to inefficient phonation and subglottal pressure compensation to regain loudness. The proposed tool is deemed sufficiently accurate and flexible for future comprehensive investigations of non-phonotraumatic vocal hyperfunction and other laryngeal motor control disorders.
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