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Research examining bilinguals who stutter (BWS) is limited; in particular there are few studies that have considered examining features of speech motor control in BWS. The present study was designed to examine features of speech motor control in bilingual speakers of Mandarin and English. Speech motor control was examined through the acoustic analysis of speaking rate, voice onset time (VOT) and stuttering adaptation. Participants ranged from age between 9 and 27 years. Upon completion of a language dominance questionnaire, two BWS participants were found to be English dominant and three were Mandarin dominant. Each BWS participant was matched to age/sex matched control participants (BWNS). Results for the BWS participants found more stuttering in the less dominant language based on a measure of percentage of syllables stuttered. All of the BWS participants demonstrated stuttering adaptation and there was no significant difference in the amount of adaptation for Mandarin and English. There was no difference found between BWS and BWNS for speaking rate and VOT. In spite of the similarity between BWS and BWNS, speaking rate in Mandarin appeared to be faster compared to English. These findings suggest that speech motor control in BWS and BWNS are similar and current application of these findings to the clinical setting is discussed.

L'objectif de ce travail, mené en partenariat avec le Département de Chirurgie Oncologique du Centre Paul Strauss à Strasbourg, est d'évaluer les conséquences d'une chirurgie thyroïdienne sur la voix des patients, afin de déceler les différentes perturbations qu'entraîne cette opération chirurgicale, et de mettre au jour les possibles stratégies de compensation ou de réajustements que le patient peut mettre en place, seul ou à l'aide d'une rééducation orthophonique ; il s'agit d'une étude longitudinale. L'évaluation reposait sur l'analyse de signaux acoustiques, à partir desquels une quantité importante d'indices relatifs à la qualité vocale, mais aussi aux comportements articulatoires des locuteurs, a pu être extraite. La production de voyelles soutenues a permis de conduire deux études spectrales. L'étude spatio-temporelle a été rendue possible grâce à l'analyse de logatomes, et plus précisément de séquences VCV. Nous avons mené trois expériences sur le plan acoustique. La première expérience traite des caractéristiques spectrales de la voix de patients ayant subi une thyroïdectomie et ne présentant pas d'immobilité laryngée. La deuxième étude est menée à partir des caractéristiques spectrales de la voix de locuteurs présentant une immobilité laryngée post-thyroïdectomie. Enfin, notre dernière expérience a pour objet, l'étude des caractéristiques spatio-temporelles de la voix de locuteurs qui ont subi une thyroïdectomie et présentant une immobilité laryngée. L'interprétation articulatoire, effectuée à partir des données acoustiques, révèle des perturbations aussi bien des gestes glottiques que des gestes supraglottiques, avec des stratégies de réajustements variables suivant les patients. La conception d'une " cible ", comme espace de contrôle pour la réalisation de possibles articulatoires et acoustiques perceptivement acceptables, semble particulièrement pertinente ici, dans la mesure où les locuteurs pathologiques réorganisent leurs productions selon leurs propres contraintes physiologiques et anatomiques, provoquées par leur pathologie.

During the course of this thesis, two scenarios are considered. In the first one, we contribute to feature extraction algorithms. In the second one, we use features to improve object detection solutions and localization. The two scenarios give rise to into four thesis sub-goals. First, we present a new shape skeleton pruning algorithm based on contour approximation and the integer medial axis. The algorithm effectively removes unwanted branches, conserves the connectivity of the skeleton and respects the topological properties of the shape. The algorithm is robust to significant boundary noise and to rigid shape transformations. It is fast and easy to implement. While shape-based solutions via boundary and skeleton analysis are viable solutions to object detection, keypoint features are important for textured object detection. Therefore, we present a keypoint featurebased planar object detection framework for vision-based localization. We demonstrate that our framework is robust against illumination changes, perspective distortion, motion blur, and occlusions. We increase robustness of the localization scheme in cluttered environments and decrease false detection of targets. We present an off-line target evaluation strategy and a scheme to improve pose. Third, we extend planar object detection to a real-time approach for 3D object detection using a mobile and uncalibrated camera. We develop our algorithm based on two novel naive Bayes classifiers for viewpoint and feature matching that improve performance and decrease memory usage. Our algorithm exploits the specific structure of various binary descriptors in order to boost feature matching by conserving descriptor properties. Our novel naive classifiers require a database with a small memory footprint because we only store efficiently encoded features. We improve the feature-indexing scheme to speed up the matching process creating a highly efficient database for objects. Finally, we present a model-free long-term tracking algorithm based on the Kernelized Correlation Filter. The proposed solution improves the correlation tracker based on precision, success, accuracy and robustness while increasing frame rates. We integrate adjustable Gaussian window and sparse features for robust scale estimation creating a better separation of the target and the background. Furthermore, we include fast descriptors and Fourier spectrum packed format to boost performance while decreasing the memory footprint. We compare our algorithm with state-of-the-art techniques to validate the results.

<p>While pronunciation has previously been described as a neglected skill in the second language classroom, a growing body of literature has demonstrated that pronunciation training improves students’ productions (Derwing & Munro, 2005). Mispronunciations have been shown to impact comprehensibility, intelligibility, and accentedness (Derwing & Munro, 2009). As pronunciation instruction methods have begun to be the subject of empirical research, Visual Feedback (VF) has begun to emerge as a novel method for teaching pronunciation. This method has been shown to be particularly effective for teaching voice onset time (VOT), a characteristic of voiceless stop consonants (e.g., /p, t, k/). Worth noting, English and Spanish differ concerning VOT, with English employing long VOTs (30-100ms) and Spanish short VOTs (0-30ms) (Lisker & Abramson’s, 1964). Previous research has focused exclusively on employing VF for shortening VOT, although there are some compelling reasons to question whether the size and nature of the effect would be similar for lengthening VOT. The present study examines the potential effectiveness of VF as a means of lengthening the VOT of Spanish learners of English.</p> <p>The participants of the study were twenty-six students from a large Colombian university. The experiment design consisted of a pretest, three VF interventions, a posttest, and a delayed posttest. The tests were composed of two tasks, differing in their complexity: recording words in isolation and words in utterances. Stimuli consisted of English words (n= 4266) with word-initial voiceless stops (/p, t, k/). Stimuli were controlled for stress, following vowel, and word familiarity  and were measured for VOT using Praat (Boersma & Weenink, 2022).</p> <p>Results from statistical analysis coupled with a visual inspection of the data indicated that the experimental group performed similarly in the three stages of the study and that the visual feedback paradigm did not result in changes in VOT. However, some degree of variation was found among the participants concerning their average VOTs. While some participants showed an overall increase (i.e., improvement) in English VOTs for the three phonemes /p/, /t/, and /k/ over time, other participants did not. In general, most of the participants produced English-like VOTs in the pretest, constituting a degree of ceiling effects. The rate of exposure to the target language and the saliency of English are factors that could have played a role in the development of the VOT scores of the participants before the study. Therefore, the discussion focuses on both the nature of the individual variability and the theoretical implications of ceiling effects found in the current study versus the lack of ceiling effects in other studies with similar populations.</p>

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<p dir="ltr">Upon acquiring or learning another language, cross-linguistic influence (CLI) is an inevitable phenomenon with which a bilingual speaker lives. One key aspect of CLI is its bidirectionality, flowing between both the first (L1) and second languages (L2) mutually affecting each other. However, investigations of L1 CLI on L2 have dominated previous bilingual studies, and despite the increasing amount of research on L2 CLI on L1, the phonetic and phonological domains remain relatively underexplored. The primary goal of the present study is to expand our understanding of the underlying mechanisms governing L2 CLI on L1 phonetics and phonology.</p><p dir="ltr">The present study investigates L2 CLI on L1 phonetics and phonology by examining both the speech perception and production of L1 sound categories among two different groups of bilinguals, Korean heritage speakers (HSs, <i>n</i> = 30) and long-term immigrants (LTIs, <i>n</i> = 27) group participants in the US, in comparison to L1(Korean)-immersed (L1-i) native speakers residing in South Korea (<i>n</i> = 30). Participants completed a series of three experimental tasks: (1) a three-alternative forced-choice (3AFC) identification task, (2) an AX discrimination task, and (3) a controlled reading paradigm task.</p><p dir="ltr">Experiment 1 (3AFC task) was conducted to investigate the extent and direction of L2 CLI in perceptual cue weighting to L1 speech categories. In this task, participants listened to a Korean word in each trial, potentially differing in the word-initial stop, and decided which word they heard from a real-word Korean minimal triplet /pul/ ‘fire,’ /p^hul/ ‘grass,’ and /p^*ul/ ‘horn.’ Specifically, the word-initial stop consisted of an eight-by-eight orthogonal voice onset time (VOT)–onset f0 continuum, created through a speech resynthesis technique. Based on the similarities and differences in the use of the two acoustic parameters between Korean (either onset f0 or VOT is a primary cue) and English stops (VOT is the primary cue), bilingual participants were expected to exhibit different cue-weighting patterns, as compared to L1-i speakers. The results from the mixed-effects logistic regression model analyses indicated that while HSs were less sensitive to the Korean primary cue, onset f0, compared to L1-i speakers—suggesting assimilation to L2 in the perceptual domain—LTIs exhibited greater sensitivity to this cue, indicating dissimilation from L2. It was also found that bilingual participants’ Korean dominance significantly influenced their cue weighting in the perception of Korean stops.</p><p dir="ltr">Experiment 2 (AX discrimination task) was administered to assess participants’ perceptual accuracy for L1 stop categories and the potential impact of L1 cue weighting, as estimated in Experiment 1, on their discrimination performance. Notably, the VOT in the stop stimuli used in the AX task were resynthesized to have a consistent VOT of 70 ms across all stimuli. This setup created a condition where participants had no choice but to rely solely on the onset f0 cue—the primary cue to the Korean lenis-aspirated stop contrast, rendering VOT, the primary cue for the voicing contrast in English stops, uninformative. The results from mixed-effects logistic regression models showed that HSs were significantly less accurate in discriminating their L1 stop categories without the VOT cue, while LTIs outperformed the L1-i speakers. That is, the LTI group, the most balanced group in terms of language dominance, had the highest accuracy in discriminating L1 contrasts among the participant groups. Furthermore, individual sensitivity to the onset f0 cue was found to be positively correlated with discrimination performance.</p><p dir="ltr">Experiment 3 (Controlled reading paradigm) aimed to examine L2 CLI on the implementation of acoustic parameters for L1 Korean stops, as well as the potential impact of proficiency and dominance on these parameters. Participants read aloud a list of minimal triplet stimuli differing in the word-initial stop within a carrier phrase. A machine-learning-based audio signal detection system was used to analyze the acoustic parameters, and Bayesian mixed-effects linear regression models, along with quadratic polynomial regression models, were implemented for statistical analysis of the processed data. The results of the production task mirrored the perception task (Experiment 1): HSs demonstrated assimilation to L2 via onset f0, while LTIs showed dissimilation, as compared to L1-i speakers. The analysis also revealed that the degree of bilingual balance in dominance and proficiency significantly influenced the implementation of onset f0, with more balanced bilinguals exhibiting greater category contrasts than less balanced bilinguals, regardless of whether they were Korean-dominant or English-dominant.</p><p dir="ltr">The findings from these experiments provide concrete evidence of L2 CLI in L1 phonetics and phonology. Importantly, the results demonstrate that not only the timing of L2 acquisition and the quantity and quality of L2 input but also the quality and quantity of L1 acquisition and bilingual balance contribute to the direction and the degree of L2 CLI in L1 speech. These findings align with the predictions of the revised Speech Learning Model (SLM-r, Flege & Bohn, 2021) and expand its scope of application to include both HSs and LTIs. In particular, the evidence of category assimilation and dissimilation lends support to the bidirectional CLI hypothesis proposed by SLM-r. To conclude, the present dissertation expands our understanding of the nature of L2 CLI in L1 phonetics and phonology in bilingual speakers.</p>

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