###### Abstract  
Unilateral vocal fold polyps can lead to incomplete glottal closure and irregular vocal fold vibration. Depending on polyp size and resulting dysphonia severity, voice therapy or surgery may be recommended. As part of voice therapy, patients may learn how to optimize intrinsic and extrinsic laryngeal muscle use to mitigate benign lesions effects, increase vocal efficiency, and improve voice quality. In this study, we used a low-dimensional mass model with a simulated unilateral vocal fold polyp and varied intra-laryngeal muscle activity to simulate vocal fold vibration across varied conditions. Differing muscle activation has different effects on frequency, periodicity, and intensity. Accordingly, learning how to optimize muscle activity in a unilateral polyp setting may help patients achieve the best possible periodic and most efficiently produced voice in the context of abnormal vocal fold morphology. vocal fold polyp; vocal fold vibration; vocal fold vibration simulation; vocal fold vibration model; aeroacoustics; larynx +
Footnote †: journal: Medical Pathology Setting on Vocal Fold Vibration. and [PERSON] [9] and later modified by [PERSON] and [PERSON] [10]. Much work has been done to couple various flow models to these two-mass models to better match physiological data. For this study, two aspects of previous models were of particular interest. One was the use of a nonlinear model to study chaotic vibration in the unilateral polyp setting, first proposed by [PERSON] et al. [11]. Nonlinear dynamic methods can be used to describe disordered voice production when vocal fold vibration is aperiodic. The influence of tension asymmetry on phonation onset, intensity, and fundamental frequency has been experimentally observed and simulated with this nonlinear model by [PERSON] [12]. [PERSON] [13] used high-speed videoendoscopy and modeling to investigate the phase asymmetry of vibration and found that vibratory asymmetries have no direct relationship with acoustic spectral tilt measures. The second relevant aspect is intrinsic laryngeal muscle activation during phonation. The intrinsic muscles interconnect the cartialages of the larynx, such as the thyravertonoid muscle, cricoarytenoid muscle, lateral cricoarytenoid muscle, and posterior cricoarytenoid muscle. Previous studies have shown direct correlations between intrinsic muscle activation and characteristics of sound production [14; 15; 16]. [PERSON] et al. [14] showed the influence of various combinations of thyravertonoid muscle, lateral cricoarytenoid muscle, and cricothyroid muscle activation on acoustic output in an in vivo canine model. [PERSON] et al. [15] also used an in vivo canine model to assess possible neuromuscular compensation mechanisms that could potentially be used in the treatment of vocal fold pathology. [PERSON] et al. [16] evaluated combinations of superior and recurrent laryngeal nerve activation to explore fundamental relations between nerve activation and laryngeal muscle activation during phonation. There are many differences between normal vocal fold and pathological vocal fold vibration. The natural frequencies of the vocal fold entail the vibration of the two lips of vocal fold to the same frequency on phonation [17; 18]. It is not clear if such entrainment occurs when a unilateral polyp is present, nor if the whole vocal fold will have the same effect when a vocal polyp is present. For a pathological vocal fold, the natural frequency differs from the normal one. Vocal polyps may affect the vocal fold vibrations and flow dynamics. Prior studies have focused more on the manipulation of normal mode frequencies, effective mass in vibration, vocal fold length, stiffness, and vocal fold thickness, which are not directly controlled by the speaker [19]. Greater attention to muscle activation may yield new insights into the physiology of disordered voice production. Current modeling guidelines for vocal fold muscle activation are mostly based on normal vibration.