Master of Science

thesisVocal hyperfunction, characterized by excessive laryngeal muscle tension, is a condition associated with numerous voice disorders, including primary muscle tension dysphonia (pMTD). Primary MTD is disturbance occurring in the absence of structural or neurologic pathology. Vocal hyperfunction is postulated to be the proximal cause of the dysphonia in pMTD. A measure of relative fundamental frequency (RFF) has been proposed as an objective and noninvasive marker of vocal hyperfunction. This retrospective study examined the clinical utility of RFF in identifying and tracking changes in vocal hyperfunction before and following a course of manual circumlaryngeal therapy for pMTD patients. Because RFF is a time-based acoustic measure reliant on periodicity for accurate calculation, additional investigation into the influence of dysphonia severity on its validity across the severity spectrum was completed. RFF calculations were derived from pre- and posttreatment audio recordings from 111 females with pMTD and 20 vocally normal controls. Three voiced-voiceless stimuli (VCV tokens) were analyzed. Listener ratings of dysphonia severity were employed to determine (1) the relation of RFF measures to overall severity, and (2) the effects of dysphonia severity on the utility of RFF calculations. Multiple regression analyses demonstrated that RFF onset slope consistently varied as a function of group membership and therapy time conditions. Pearson Product-Moment Correlations showed a significant relationship between RFF onset cycle 1 values and listener ratings of dysphonia severity. In addition, regression analysis confirmed the influence of therapy condition and specific RFF cycles on dysphonia severity rating. Cumulatively, the analyses confirmed that RFF onset may be sensitive to predicting the presence and degree of vocal hyperfunction before and after therapy, and as an index of dysphonia severity. However, RFF could not be fully analyzed in many subjects, yielding a large quantity of missing data. Adjusted odds ratio estimates revealed that these unanalyzable data were related to phonetic context (token), group membership (pMTD vs. control) and severity level of dysphonia. Although RFF showed potential as an objective measure of vocal hyperfunction before and following voice therapy, the large number of unanalyzable samples (related to increased dysphonia severity especially in the pMTD group) represents a critical limitation

Analysis of Disengagements in Semi-Autonomous Vehicles: Drivers’ Takeover Performance and Operational Implications

This report analyzes the reactions of human drivers placed in simulated Autonomous Technology disengagement scenarios. The study was executed in a human-in-the-loop setting, within a high-fidelity integrated car simulator capable of handling both manual and autonomous driving. A population of 40 individuals was tested, with metrics for control takeover quantification given by: i) response times (considering inputs of steering, throttle, and braking); ii) vehicle drift from the lane centerline after takeover as well as overall (integral) drift over an S-turn curve compared to a baseline obtained in manual driving; and iii) accuracy metrics to quantify human factors associated with the simulation experiment. Independent variables considered for the study were the age of the driver, the speed at the time of disengagement, and the time at which the disengagement occurred (i.e., how long automation was engaged for). The study shows that changes in the vehicle speed significantly affect all the variables investigated, pointing to the importance of setting up thresholds for maximum operational speed of vehicles driven in autonomous mode when the human driver serves as back-up. The results shows that the establishment of an operational threshold could reduce the maximum drift and lead to better control during takeover, perhaps warranting a lower speed limit than conventional vehicles. With regards to the age variable, neither the response times analysis nor the drift analysis provide support for any claim to limit the age of drivers of semi-autonomous vehicles

The effects of linguistic factors on analysis of relative fundamental frequency in typical speakers

Thesis (M.S.)--Boston UniversityResearch has shown that the relative fundamental frequency (RFF) surrounding voiceless obstruents may be used as an acoustic correlate for laryngeal tension. This suggests that RFF could potentially be used as a measurement of vocal hyperfunction, a voice pathology characterized by overexertion and increased tension ofthe laryngeal muscles. Despite this potential relationship between laryngeal tension and RFF, there has been little research into what factors contribute to creating stimuli that effectively produce reliable and valid RFF data for subsequent analyses. This study sought to investigate the impacts that linguistic factors have on RFF elicitation in healthy speakers. Two hypotheses were tested: Whether there is a significant difference across voiceless obstruents (i.e. /f/, /s/, /∫/, /k/, /t/, /p/) in terms of eliciting consistent RFF values, and whether sentences containing just one voiceless obstruent or many voiceless obstruents (i.e. "unmixed" vs. "mixed" sentences) are more effective in eliciting stable RFF. Twenty-eight sentences were developed, each containing 3-6 instances of RFF; there were 18 "unmixed" sentences, sub-grouped by obstruent, and 10 "mixed" sentences containing a variety of voiceless obstruents in each sentence. Twelve healthy adults were recorded producing this corpus of sentences and these samples were analyzed using acoustic analysis software. Results of this analysis showed that there were statistically significant differences across the voiceless obstruents in terms of producing consistent, stable instances of RFF, and that the differences appeared to be connected to the manner of articulation of the obstruent (i.e. fricatives were more stable than stops). No significant difference was noted between the types of sentences (i.e. mixed vs. unmixed) but qualitative differences were noted between the two groups (e.g., increased data loss in the mixed sentence group due to increased frequency of vocal irregularities). These results provide some insight into the factors that contribute to creating effective stimuli for eliciting reliable and valid RFF, and the information gathered should be taken into consideration for future studies

Speaker-sex discrimination for voiced and whispered vowels at short durations

Whispered vowels, produced with no vocal fold vibration, lack the periodic temporal fine structure which in voiced vowels underlies the perceptual attribute of pitch (a salient auditory cue to speaker sex). Voiced vowels possess no temporal fine structure at very short durations (below two glottal cycles). The prediction was that speaker-sex discrimination performance for whispered and voiced vowels would be similar for very short durations but, as stimulus duration increases, voiced vowel performance would improve relative to whispered vowel performance as pitch information becomes available. This pattern of results was shown for women’s but not for men’s voices. A whispered vowel needs to have a duration three times longer than a voiced vowel before listeners can reliably tell whether it’s spoken by a man or woman (∼30 ms vs. ∼10 ms). Listeners were half as sensitive to information about speaker-sex when it is carried by whispered compared with voiced vowels

Optimization and automation of relative fundamental frequency for objective assessment of vocal hyperfunction

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

Voice initiation and voice offset patterns in normal females: investigated by high speed digital imaging

This preliminary study investigated the voice initiation period (VIP) and voice offset period (VOP) using high-speed digital imaging. The purpose of the study was to obtain preliminary data on VIP and VOP patterns of normal voice and to investigate the variability in VIP and VOP patterns in young female subjects within and between recording sessions. VIP was segmented into 3 phases: VIPa, VIPb, and VIPc. Results of the analysis of the data demonstrated that VOP is a more consistent measure than VIP and that VIPa is the most consistent phase of VIP. This study also suggested that changes in fundamental frequency and intensity may affect the number of glottic cycles necessary to complete VIP segments but not the VOP

The relationships among physiological, acoustical, and perceptual measures of vocal effort

The purpose of this work was to explore the physiological mechanisms of vocal effort, the acoustical manifestation of vocal effort, and the perceptual interpretation of vocal effort by speakers and listeners. The first study evaluated four proposed mechanisms of vocal effort specific to the larynx: intrinsic laryngeal tension, extrinsic laryngeal tension, supraglottal compression, and subglottal pressure. Twenty-six healthy adults produced modulations of vocal effort (mild, moderate, maximal) and rate (slow, typical, fast), followed by self-ratings of vocal effort on a visual analog scale. Ten physiological measures across the four hypothesized mechanisms were captured via high-speed flexible laryngoscopy, surface electromyography, and neck-surface accelerometry. A mixed-effects backward stepwise regression analysis revealed that estimated subglottal pressure, mediolateral supraglottal compression, and a normalized percent activation of extrinsic suprahyoid muscles significantly increased as ratings of vocal effort increased (R2 = .60). The second study had twenty inexperienced listeners rate vocal effort on the speech recordings from the first study (typical, mild, moderate, and maximal effort) via a visual sort-and-rate method. A set of acoustical measures were calculated, including amplitude-, time-, spectral-, and cepstral-based measures. Two separate mixed-effects regression models determined the relationship between the acoustical predictors and speaker and listener ratings. Results indicated that mean sound pressure level, low-to-high spectral ratio, and harmonic-to-noise ratio significantly predicted speaker and listener ratings. Mean fundamental frequency (measured as change in semitones from typical productions) and relative fundamental frequency offset cycle 10 were also significant predictors of listener ratings. The acoustical predictors accounted for 72% and 82% of the variance in speaker and listener ratings, respectively. Speaker and listener ratings were also highly correlated (average r = .86). From these two studies, we determined that vocal effort is a complex physiological process that is mediated by changes in laryngeal configuration and subglottal pressure. The self-perception of vocal effort is related to the acoustical properties underlying these physiological changes. Listeners appear to rely on the same acoustical manifestations as speakers, yet incorporate additional time-based acoustical cues during perceptual judgments. Future work should explore the physiological, acoustical, and perceptual measures identified here in speakers with voice disorders.2019-07-06T00:00:00

Voice Onset Time Enhanced User System (VOTEUS): a web graphic interface for the analysis of plosives’ release phases

The paper proposes an up-to-date literature review of the works using AutoVOT, a discriminative large-margin learning algorithm developed for the semi-automatic measurement of voice onset times. In order to expand the accessibility of the tool in linguistic research, we present VOTEUS, a user-friendly graphic interface written in Python. The interface is conceived to assist the researcher throughout the whole process of annotation, from the forced alignment of the corpora to the refinement of the AutoVOT tier and the extraction of the durations. The general aim is to speed up this phase of data analysis, providing a significant improvement on prevalent practice to date