abstract: Speech intelligibility measures how much a speaker can be understood by a listener. Traditional measures of intelligibility, such as word accuracy, are not sufficient to reveal the reasons of intelligibility degradation. This dissertation investigates the underlying sources of intelligibility degradations from both perspectives of the speaker and the listener. Segmental phoneme errors and suprasegmental lexical boundary errors are developed to reveal the perceptual strategies of the listener. A comprehensive set of automated acoustic measures are developed to quantify variations in the acoustic signal from three perceptual aspects, including articulation, prosody, and vocal quality. The developed measures have been validated on a dysarthric speech dataset with various severity degrees. Multiple regression analysis is employed to show the developed measures could predict perceptual ratings reliably. The relationship between the acoustic measures and the listening errors is investigated to show the interaction between speech production and perception. The hypothesize is that the segmental phoneme errors are mainly caused by the imprecise articulation, while the sprasegmental lexical boundary errors are due to the unreliable phonemic information as well as the abnormal rhythm and prosody patterns. To test the hypothesis, within-speaker variations are simulated in different speaking modes. Significant changes have been detected in both the acoustic signals and the listening errors. Results of the regression analysis support the hypothesis by showing that changes in the articulation-related acoustic features are important in predicting changes in listening phoneme errors, while changes in both of the articulation- and prosody-related features are important in predicting changes in lexical boundary errors. Moreover, significant correlation has been achieved in the cross-validation experiment, which indicates that it is possible to predict intelligibility variations from acoustic signal. / Dissertation/Thesis / Doctoral Dissertation Speech and Hearing Science 2019

La paralysie cérébrale est la pathologie motrice la plus commune dans l’enfance, elle engendre tous types de troubles principalement moteurs. La parole peut notamment être touchée affectant parfois profondément les capacités communicatives des enfants. Les thérapies pour pallier les troubles moteurs de la parole manquent d’efficacité. C’est dans ce cadre que le logiciel RePliCa a été développé afin de rendre leur rééducation plus efficiente. Une variable, encore peu documentée dans le cadre de la rééducation, est identifiée comme influençant grandement les progrès, il s’agitde l’engagement. L’engagement est considéré comme malléable et sensible aux changements environnementaux et pourrait donc être influencé par l’introduction d’un logiciel dans la rééducation. La première partie de cette thèse était consacrée à l’optimisation de cet outil. Dans cet objectif, une série d’études expérimentales a été menée auprès d’enfants au développement typique et a permis l’intégration d’un certain nombre de caractéristiques relatives à l’interface influençant positivement l’engagement. Une grille d’observation a ensuite été créée afin d’évaluer l’engagement des enfants paralysés cérébraux dans la rééducation lors du programme pilote avec le logiciel. L’étude clinique montre des résultats encourageants, l’engagement semblant se maintenir au cours des séances. Ces résultats sont mis en perspectives dans le cadre d’un modèle de l’engagement. / Cerebral Palsy is the most common physical disability in early childhood, resulting in multiple disorders, primarily of motor skills. Speech especially can be impacted and deeply affects children’s communicative abilities. The RePliCa software wasdeveloped to improve the efficiency of motor speech therapy. One variable, engagement, has not been fully researched in the field of rehabilitation but has been identified influential for children’s progress. Engagement is presumed to bemalleable and sensitive to environmental changes and therefore could be influenced by the introduction of software in rehabilitation. The first part of this thesis was devoted to its optimization. To this end, a series of experimental studies wereconducted, enabling the integration of a number of features on the interface in order to promote engagement. Once the software was implemented, engagement in rehabilitation was examined in a clinical study. Results showed encouraging results: engagement can be maintained over time. Results are put in perspective using an engagement model framework

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The overarching goal of this dissertation was to assess a set of sensorimotor, acoustic, and functional speech measures to inform the understanding of the mechanisms underlying two common speech disorders with evidence of disrupted sensory function: hyperfunctional voice disorders (HVDs) and hypokinetic dysarthria resulting from Parkinson’s disease (PD). The purpose of the first and second study was to elucidate the mechanisms underlying speech symptoms in HVDs. The aim of the first study was to examine whether auditory discrimination and vocal responses to altered auditory feedback (indicative of vocal motor control) differed in a large set of speakers with HVDs (N = 62) compared to controls (N = 62). The results directly implicate disrupted auditory processing in impairments to vocal motor control in HVDs. Building on this finding, the second study sought to compare the same auditory and vocal motor control measures in speakers with HVDs pre- and post-therapy (N = 11) to assess whether successful therapy (i.e., voice symptom improvement) resulted in improvements to auditory-motor function. On average, vocal motor control improved after therapy but there were little changes to measures of auditory processing, which suggests that therapeutic improvements in HVDs may be compensatory rather than a result of resolving the underlying auditory processing deficits. The collective findings from the first and second study improve the understanding of the development of HVDs and highlight the need to consider auditory processing in assessment and treatment of HVDs. The third and fourth study objectives were to characterize auditory-motor control and longitudinal changes to speech acoustics in PD. In the third study, auditory-motor control of both voice and articulatory parameters of speech were assessed in speakers with PD on medication (N = 28) compared to controls (N = 28) and compared to measures of speech function (intelligibility and naturalness ratings). No group differences were found in auditory-motor measures, regardless of speech domain. These results, which describe findings from the largest sample of PD patients completing auditory-motor tasks to-date (N=28), suggest that auditory-motor control is intact in individuals with PD on their typical medication cycle. This work also provided the first evidence that auditory-motor measures reflect measures of speech function (speech intelligibility and naturalness). The fourth and final study in this dissertation examined whether longitudinal changes to speech acoustics in PD were associated with the specific time (in months) between speech samples. Although prior work has examined speech decline in PD, no study to-date has assessed whether speech acoustics are sensitive to disease progression within an individual with PD. The current study examined acoustic speech samples collected from speakers with PD (N = 30) at two separate time points. Longitudinal changes to speech acoustics were examined by time between speech samples, motor phenotype and sex assigned at birth, to shed light on the relationships between acoustic measures of speech, disease progression, motor symptoms, and sex. The study revealed that longitudinal decline in second formant slope, articulation rate (syllables per second) across The Rainbow Passage, and relative fundamental frequency offset values were all associated with increased time between sessions within a speaker. In addition, longitudinal increases in percent pause time in conversational speech were more likely in the PIGD motor phenotype, and longitudinal increases mean fo across conversational speech were more likely in males compared to females with PD. This work provides the first report of acoustic measures of speech that reflect the specific time, in months, of PD progression, as well as acoustic measures of speech that appear to be differentially impacted over time by motor phenotype and by sex. The findings provide evidence that three acoustic measures of speech show promise as measures of PD progression in months and support the notion that speech symptom decline differs by motor phenotype and by sex assigned at birth, which should be considered when planning therapeutic interventions. / 2026-08-31T00:00:00Z

The purpose of this study was to examine how a critical principle of motor learning, practice amount (high number of trials versus a low number of trials), affects speech motor learning in childhood apraxia of speech (CAS). It also sought to contribute to the literature base regarding using an integral stimulation approach for these children. Currently, a limited evidence base exists for decision-making regarding practice amount in CAS treatment. Using a single-case experimental design with two participants, three target sets of utterances (High Amount, Low Amount, and Control) received different amounts of treatment. Outcomes were compared in terms of retention. Targets were scored regarding perceptual (prosodic and segmental) accuracy. Effect sizes were computed to quantify the extent of treatment effects. For both participants, results show some evidence suggesting a higher amount of practice is advantageous and leads to greater learning. A low amount of treatment did not show clear differences compared to not receiving any treatment. Caution should be taken when interpreting these findings due to its small sample size and modest effects. Results suggest that the integral stimulation approach may only be effective if provided with a significantly high amount of practice. Further research is needed to examine how the principles of motor learning and the integral stimulation approach should be sensibly and systematically applied to promote best outcomes for this population. / Communication Sciences

This study presents detailed phonetic and acoustic analyses of the speech characteristics of two new cases of Foreign Accent Syndrome (FAS). Participants include a 48-year-old female who began speaking with an "Eastern European" accent following a traumatic brain injury, and a 45-year-old male who presented with a "British" accent following a subcortical cerebral vascular accident (CVA). Identical samples of the participants' pre- and post-morbid speech were obtained, thus affording a new level of control in the study of Foreign Accent Syndrome. The speech tasks consisted of oral readings of the Grandfather Passage and 18 real words comprised of the stop consonants /p/, /t/, /k/, /b/, /d/, /g/ combined with the peripheral vowels /i/, /a/ and /u/ and ending in a voiceless stop. Computer-based acoustic measures included: 1) voice onset time (VOT), 2) vowel durations, 3) whole word durations, 4) first, second and third formant frequencies, and 5) fundamental frequency. Formant frequencies were measured at three points in the vowel duration: a) 20%, b) 50%, and c) 80% to assess differences in vowel 'onglides' and 'offglides'. The phonetic analysis provided perceptual identification of the major phonetic features associated with the foreign quality of participant's FAS speech, while acoustic measures allowed precise quantification of these features. Results indicated evidence of backing of consonant and vowel productions for both participants. The implications for future research and clinical applications are also considered.