The project objective is to improve clinical assessment and diagnosis of the voice disorder, vocal hyperfunction (VH). VH is a condition characterized by excessive laryngeal and paralaryngeal tension, and is assumed to be the underlying cause of the majority of voice disorders. Current clinical assessment of VH is subjective and demonstrates poor inter-rater reliability. Recent work indicates that a new acoustic measure, relative fundamental frequency (RFF) is sensitive to the maladaptive functional behaviors associated with VH and can potentially be used to objectively characterize VH. Here, we explored and enhanced the potential for RFF as a measure of VH in three ways. First, the current protocol for RFF estimation was optimized to simplify the recording procedure and reduce estimation time. Second, RFF was compared with the current state-of-the-art measures of VH – listener perception of vocal effort and the aerodynamic ratio of sound pressure level to subglottal pressure level. Third, an automated algorithm that utilized the optimized recording protocol was developed and validated against manual estimation methods and listener perception. This work enables large-scale studies on RFF to determine the specific physiological elements that contribute to the measure’s ability to capture VH and may potentially provide a non-invasive and readily implemented solution for this long-standing clinical issue.

Relative fundamental frequency (RFF) is an acoustic measure that quantifies short-term changes in fundamental frequency during voicing transitions surrounding a voiceless consonant. RFF is hypothesized to be decreased by increased laryngeal tension during voice production and has been considered a potential objective measure of vocal hyperfunction. Previous studies have supported claims that decreased RFF values may indicate the severity of vocal hyperfunction and have attempted to improve the methods to obtain RFF. In order to make progress towards developing RFF into a clinical measure, this dissertation aimed to investigate further the validity and reliability of RFF. Specifically, we examined the underlying physiological mechanisms, the auditory-perceptual relationship with strained voice quality, and test-retest reliability. The first study evaluated one of the previously hypothesized physiological mechanisms for RFF, vocal fold abduction. Vocal fold kinematics and RFF were obtained from both younger and older typical speakers producing RFF stimuli with voiceless fricatives and stops during high-speed videoendoscopy. We did not find any statistical differences between younger and older speakers, but we found that vocal folds were less adducted and RFF was lower at voicing onset after the voiceless stop compared to the fricative. This finding is in accordance with the hypothesized positive association between vocal fold contact area during voicing transitions and RFF. The second study examined the relationship between RFF and strain, a major auditory-perceptual feature of vocal hyperfunction. RFF values were synthetically modified by exchanging the RFF contours between voice samples that were produced with a comfortable voice and with maximum vocal effort, while other acoustic features remained constant. We observed that comfortable voice samples with the RFF values of maximum vocal effort samples had increased strain ratings, whereas maximum vocal effort samples with the RFF values of comfortable voice samples had decreased strain ratings. These findings support the contribution of RFF to perceived strain. The third study compared the test-retest reliability of RFF with that of conventional voice measures. We recorded individuals with healthy voices during five consecutive days and obtained acoustic, aerodynamic, and auditory-perceptual measures from the recordings. RFF was comparably reliable as acoustic and aerodynamic measures and more reliable than auditory-perceptual measures. This dissertation supports the translational potential of RFF by providing empirical evidence of the physiological mechanisms of RFF, the relationship between RFF and perceived strain, and test-retest reliability of RFF. Clinical applications of RFF are expected to improve objective diagnosis and assessment of vocal hyperfunction, and thus to lead to better voice care for individuals with vocal hyperfunction. / 2021-09-25T00:00:00Z

The exploration of underlying pathophysiology of speech disorders is hampered by the limitations in quantitative assessment of speech production. Current assessments are driven by measures that couple underlying processes of speech production with mechanisms that compensate for speech deficits. We propose a multifactorial approach to decouple these effects and examine underlying processes of speech motor control. In study 1 we conducted a sensorimotor characterization of speech motor control via altered sensory feedback techniques. We applied these measures to investigate effects of dopaminergic medication on laryngeal and articulatory motor control mechanisms in persons with Parkinson’s disease (PwPD). The study outcomes provide preliminary indication that dopaminergic medication may have a differential effect on laryngeal sensorimotor function in PwPD, with a normalization (reduction of atypically large responses) of auditory reflexive responses and an exacerbation (further reduction of atypically small responses) of auditory adaptive responses. The study outcomes also provide insight into the differential effects of dopaminergic medication on laryngeal and articulatory speech subsystems in PwPD. We hope the outcomes will eventually serve as a basis for designing better therapeutics focused on ameliorating voice and speech dysfunctions in PwPD. In study 2 we investigated laryngeal motor control in a population of individuals with and without hyperfunctional voice disorders (HVDs) using three different laryngeal kinematic measures extracted via high-speed video endoscopy techniques. We applied these measures to investigate differential effects of laryngeal tension, movement variability, and movement asymmetry present in individuals with HVDs. Results indicate that individuals with HVDs exhibit statistically significantly higher kinematic stiffness, spatiotemporal indices, and asymmetry indices across rate and effort conditions compared to controls, indicating higher laryngeal tension, production variability, and movement asymmetry. Laryngeal kinematics suggest differing underlying motor control strategies in individuals with HVD relative to controls, which may inform better understanding of the etiology of HVDs. The study outcomes also provide insight into the ability of laryngeal kinematics to differentiate underlying motor control strategies in individuals with various voice disorders with neurological and physiological pathophysiology that could provide crucial insight to guide future clinical intervention. In study 3, a novel neurocomputational model was developed, combining an established neurological framework of speech motor control, with a physics based vocal fold model. This numerical model decouples the neurological and physiological aspects of laryngeal motor control to provide important directions in expanding the understanding of the underlying pathophysiology of laryngeal motor control in PD and HVDs. The model has demonstrated capability to simulate different modes of laryngeal motor control, ranging from short-term (i.e., reflexive) and long-term (i.e., adaptive) auditory feedback paradigms, to generating prosodic contours in speech. LaDIVA can be used to expand the understanding of the physiology of human phonation to enable, for the first time, the investigation of causal effects of neural motor control in the fine structure of the vocal signal. / 2025-02-20T00:00:00Z

PURPOSE: Vocal hyperfunction (VH) is considered a functional voice disorder, resulting in voice complaints of hoarseness and fatigue; however, recent work suggests that voice changes in VH may result from impairments in the neural control of voice (specifically, how voice perception is integrated into voice production). This study sought to clarify whether impaired auditory acuity of vocal pitch and the temporal production of voice, two known impairments in speakers with VH, were correlated. METHOD: The current study included 29 adults with VH. Vocal auditory perception was assessed via acuity to self-produced vocal pitch (quantified using an adaptive two-forced-choice paradigm). To investigate temporal acoustic measures of voice production, voice onset time (VOT) variability of voiced and voiceless stop consonants in a carrier phrase were separately assessed using a coefficient of variation (CoV). Two Pearson product-moment correlations were completed to assess the relationship between these measures of vocal perception and vocal production of either voiced or voiceless VOTs. RESULTS: No statistically significant correlations were observed between auditory acuity and CoV of VOT for neither voiced nor voiceless stop consonants. CONCLUSION: The current findings suggest that impairments in vocal pitch acuity and VOT production in VH are not governed by the same underlying mechanism. Further investigation is recommended to determine the etiology driving these vocal perception- and production-based impairments observed in prior work.