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This study examined the differences between normal vocal fold vibration and the movement patterns of vocal folds with mass lesions by means of a synthetic model. The experimenter molded and cast three sets of vocal folds, representing normal structure, small nodules, and larger nodules. Acoustic, aerodynamic, and digital video signals were recorded and analyzed in order to quantify air flow and pressure, measure vibratory stability, and visually assess closure patterns across the three structural conditions. Statistical analysis revealed that the presence of vocal nodules resulted in a significantly higher onset pressure, fundamental frequency, airflow at onset, and offset pressure. However, the results were inconclusive with regard to vocal stability, and it remains unclear whether the current models of nodules are sufficiently similar to the human system to adequately model the type of mass lesions typically seen in a clinical context.

The voice plays a vital role in human communication. The purpose of voice research is to advance the understanding of voice production physics, with the ultimate goal of leading to improved voice care. In this research computational and synthetic vocal fold models were used to explore the role of subglottal geometry in vocal fold vibration. Three specific studies were performed. First, the effect of the inferior vocal fold surface angle on voice production was investigated using a two-dimensional self-oscillating finite element vocal fold model. Varying the inferior angle resulted in significant changes to model vibratory motion, glottal width, flow rate, and energy transfer. The changes were attributed primarily to changes in structural, rather than aerodynamic, factors. Second, subglottic stenosis (SGS) was introduced and parametrically varied in a similar computational model to determine the influence of SGS on vocal fold vibration. High severities of SGS influenced several factors related to vibration, including glottal width, flow rate, flow resistance, and vibration frequency. Subglottal pressure distributions and flow patterns were also affected. Third, the response of a self-oscillating silicone vocal fold model to varying degrees of SGS in an experimental setup was studied. Consistent with the computational SGS study, SGS had an effect on the synthetic model response at high severities. Changes were seen particularly in subglottal pressure and radiated acoustic sound, and consequently glottal efficiency, which may have important implications regarding the effect of SGS on the human voice.

Self-efficacy is theorized to represent our ability, capability, or capacity to accomplish particular tasks. One’s belief in that ability (self-efficacy belief) has been identified as the greatest predictor of successful performance and is influenced by four primary sources (enactive mastery experience, vicarious experience, verbal/social persuasion, physiological and affective states), in addition to personal and contextual influences. However, the development of accurate self-perceptions may be particularly challenging for the collegiate vocalist. In the development of singing technique—where self-assessment is complicated by the corporal nature of the vocal instrument—Bandura’s (1997) sources of self-efficacy provide a framework whereby assessment of ability and capability may become more tangible. The aim of the present study, therefore, was to investigate how collegiate vocal students’ beliefs in their vocal performance abilities may be influenced by the four self-efficacy sources and personal/contextual factors. I distributed the Vocal Performance Self-Efficacy Survey (adapted from Zelenak, 2011) to 46 voice majors at a private university in the western United States. Nine interview participants, who represented diversity of performance beliefs, were subsequently selected from the survey participant pool. Interview participants completed an initial interview based on a priori themes (four sources of self-efficacy); and a follow-up interview, which explored contextual factors (i.e., student/teacher relationship, environment, cognitive self-regulation, practice habits, and gender). In addition, participants documented three experiences—in a voice lesson, practice session, and performance—that fostered or hindered their performance belief. Vocal students in this study described how they progressed in self-belief by moving from a reliance on external assessments of ability to a reliance on self-appraisal as they (a) developed their technique through practice, studio learning, and performance (enactive mastery experience); (b) watched coping and master models (vicarious experience); (c) received feedback (verbal/social persuasion); (d) knew and felt physically when they were singing freely (physiological and affective states); and (e) learned to exercise agency (cognitive self-regulation). A particularly important finding from this study was the common and consistent reliance singers placed on physiological and affective states. Eight of nine interview participants responded that, of all the self-efficacy sources, physiological and affective states most affected their performance belief. Interview data indicate the importance of nurturing vocal students’ performance beliefs through utilizing the four sources of self-efficacy, fostering qualities of persistence and resilience, facilitating cognitive self-regulation, working toward productive student/teacher relationships, and creating safe learning and performance environments.

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.

Research on voice change in males has generally fallen into two categories: music education studies of changes in the singing voice and speech studies of changes in the speaking voice. These studies rarely consider differences in the dynamic ability of male singers at different stages of vocal development. The concept of tessitura, a portion of the vocal range in which the singer sounds best, is referred to in the literature on vocal music, but the means for identifying its size and location within the range have not been consistently specified. Tessitura appears to be a portion of the range which is most controllable in terms of dynamics and agility and is optimal in tonal quality. This study used the phonetograph to investigate differences in measures of intensity control between pre-pubertal, pubertal (changing) and post-pubertal voices in 48 males aged 9 to 18 years old. These intensity measures were compared to ratings of vocal effort from a panel of 4 music educators in order to determine if tessitura could be identified from acoustic and perceptual evidence of an optimum vocal area. Results of the study were: 1) post-pubertal voices demonstrated greater control of vocal intensity as revealed in lower mean minimum and comfortable intensity measures, higher overall maximum intensity measures and a larger minimum-to-maximum intensity range; 2) intensity measures for pubertal voices were similar to those observed in pre-pubertal voices, contrary to trends suggested in the literature on voice change; 3) the Greatest Dynamic Range (GDR) on the phonetograph, indicating the range in which singers had the most dynamic control, was smaller than the range in which the singers were judged to sound best; 4) tessitura originated in the lower portion of the vocal range, around the location of mean speaking fundamental frequency. Although registers were not specifically investigated, tessitura appeared to be primarily related to modal register in singers who had completed voice change.

In this thesis I share my journey of building my identity and confidence as a jazz vocalist. A transformational work that has served as a steppingstone for my continuous artistic work as both a vocal jazz soloist and ensemble singer. I started with a broad sense of wanting to examine the differences between solo singing and ensemble singing in jazz. This purpose was turned over, transformed, and changed several times to the very end, when I instead realized that what I truly needed to do, in this text, was to focus on myself and my own artistry. In the beginning of these studies, I had identified specific challenges and areas where I experienced difficulties in my singing and performing. During this work I summarized them in the following categories or areas: my voice, my musicianship, and my mind and mindset. I have been exploring these areas using feedback loops with performative documentation, as well as alternating between writing and reflecting, with the purpose of beginning to clarify my aesthetics and artistic choices and building my identity and self-assurance. This work resulted in my exam concert and the recording of two albums: “Unraveling” as a soloist, and “New Horizon” as an ensemble singer with Stockholm Voices. Besides these artistic results, I have reached a higher level of vocal freedom and control. I have made myself more aware of my aesthetic judgments both as a soloist an ensemble singer, and I feel I have reached a higher level of awareness, expression, and communication as a performer. Furthermore, I developed strategies for dealing with self-doubt and lack of confidence.

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