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<div>This thesis research was motivated by the need for increasing speech transmission rates through a phonemic-based tactile speech communication device named TAPS (TActile Phonemic Sleeve). The device consists of a 4-by-6 tactor array worn on</div><div>the forearm that delivers vibrotactile patterns corresponding to English phonemes. Three studies that proceeded this thesis evaluated a coding strategy that mapped 39 English phonemes into vibrotactile patterns. This thesis corresponds to a continuation of the project with improvements summarized in two parts. First, a design and implementation of a training framework based on theories of second language acquisition and game-based learning is developed. A role playing game named Haptos was designed to implement this framework. A pilot study using the first version of the game showed that two participants were able to master a list of 52 words within 45 minutes of game play. Second, an improved set of haptic codes was designed. The design was based on the statistics of spoken English and included an additional set of codes that abbreviate the most frequently co-occurring phonemes in duration. The new set included 39 English phonemes and 10 additional abbreviated symbols. The new codes represent a 24 to 46% increase in word presentation rates. A second version of the Haptos game was implemented to test the new 49 codes in a learning curriculum distributed over multiple days. Eight participants learned the new codes within 6 hours of training and obtained an average score of 84.44% in symbol identification tests with error rates per haptic symbol below 18%. The results demonstrate the feasibility of employing the new codes for future work where the ability to receive longer sequences of phonemes corresponding to phrases and sentences will be trained and tested.</div>

<div><b>Purpose:</b> Previous studies have shown that children with SSD speaking a language other than English produce different types of speech errors, although there is a paucity of information investigating these differences in speech sound production (e.g., Core & Scarpelli, 2015; Fabiano-Smith & Goldstein, 2010b; Fabiano-Smith & Hoffman, 2018). This study investigates the types of speech errors produced by bilingual Spanish-English and monolingual English-speaking children matched on age, receptive vocabulary, and articulation accuracy in single words.</div><div><br></div><div><b>Methods: </b>Twelve bilingual English-Spanish speaking children, ages 4;0 to 6;11, were matched to twelve monolingual English-Speaking children. Participants completed standardized and non-standardized tests of speech and language, and performance between groups and assessment measures were compared. Consonant sound productions were categorized as correct, substitution errors, omission errors, or distortion errors.</div><div><br></div><div><b>Results: </b>Bilingual Spanish-English children were significantly more likely than monolingual English children to produce omission errors, while monolingual English children were more likely to produce distortion errors. Both groups produced similar proportions of substitution errors. Bilingual children produced similar proportions of each error type in both of their languages.</div><div><br></div><div><b>Conclusion: </b>SLPs should not rely on English normative data to diagnose SSDs in monolingual and bilingual Spanish-speaking children, as they demonstrate different errors patterns from monolingual English-speakers.</div>

<p dir="ltr">Comprehensibility refers to the degree of effort that a listener requires to understand a speaker’s utterance (Derwing & Munro, 1997; Munro & Derwing, 1995; Derwing & Munro, 2005). Previous studies on L2 pronunciation have found that segmental errors could affect comprehensibility (Derwing et al., 1998; Derwing & Munro, 1997; Isaacs & Thomson, 2020; Saito et al., 2017). However, this finding only indicates a correlation between the number of segmental errors and lower comprehensibility. It is still unclear what aspects of pronunciation L2 learners need to practice in order to improve the comprehensibility of their speech. This thesis proposes that the degree of acoustic contrast may play a role in determining comprehensibility. More specifically, it investigates the relation between Mandarin speakers’ acoustic contrast between tense and lax vowels in English (i.e., [i] and [ɪ], [u] and [ʊ]) and the perceived comprehensibility of their speech.</p><p dir="ltr">A sentence production task and a comprehensibility rating task were conducted. In the sentence production task, 20 Mandarin speakers and 10 English speakers read aloud English sentences containing tense and lax vowels and were audio-recorded. The acoustic measurements of the vowels were taken in order to compare Mandarin speakers’ acoustic realization of the tense and lax vowels with English speakers’ productions. In the comprehensibility rating task, 48 English speakers transcribed the sentences recorded during the sentence production task and rated the comprehensibility of the sentences. The comprehensibility ratings were tested for correlation with the number of transcription errors, the degree of spectral and durational contrasts between vowels, and the speakers’ US residency length, in order to investigate the relation between intelligibility errors and comprehensibility, between acoustic contrast and comprehensibility, and between US residency length and comprehensibility.</p><p dir="ltr">The results of the linear-mixed effect model indicated that spectral contrast between [u] - [ʊ], but not [i] - [ɪ], was significantly reduced in Mandarin speakers’ productions compared to the English speakers, suggesting that Mandarin speakers under-differentiated the back vowel pair. A correlation test using Kendall’s <i>tau</i> indicated a significant negative correlation between number of intelligibility errors and comprehensibility, suggesting that intelligibility errors decreased comprehensibility. A correlation test using Kendall’s <i>tau</i> indicated a significant positive correlation between the degree of spectral contrast and comprehensibility rating for sentences with semantically meaningful context, suggesting that increasing the contrast between tense and lax vowels could help increase the comprehensibility of speech. Finally, a correlation test using Kendall’s <i>tau</i><i> </i>indicated no significant correlation between US residency length and comprehensibility, meaning that the relation between residency length and comprehensibility was not confirmed.</p><p dir="ltr">To sum up, acoustic contrast could be one of the contributors to speech comprehensibility. Therefore, directing English L2 learners to focus on increasing the acoustic distance between contrasting vowels could prove a fruitful strategy for improving the comprehensibility of L2 speech.</p>

<p dir="ltr">Bilingualism is defined as the regular use of two or more languages by a single speaker in their everyday lives (Grosjean, 2008). Prior research at the phonetic level has shown that bilinguals often experience a degree of cross-linguistic interference, in which the productions of one language shift in the direction of the opposite language. Evidence for cross-linguistic interference is most notable in contexts where bilinguals activate both of their languages, as in cases of code-switching. Yet prior research has produced somewhat mixed results, with a subset of studies failing to find evidence of cross-linguistic interference. While some authors have suggested that such mixed results may be the result of varying levels of phonetic awareness (i.e., knowledge about the phonetic norms of each language), the potential contribution of this variable has yet to be systematically explored. Utilizing code-switching as a tool, the current study examined the role of phonetic awareness in modulating bilingual cross-linguistic phonetic interaction. A total of 20 L1 Mandarin–L2 English bilinguals were recruited for a lab-based speech production paradigm. English vowel /æ/, which differs acoustically in the vowel height (F1) and vowel backness (F2) from its Mandarin counterpart /e/, was selected as the measure of the phonetic interference. Participants produced stimuli across six contexts: monolingual Mandarin, code-switched Mandarin, pre-switched Mandarin, monolingual English, code-switched English, and pre-switched English. Phonetic awareness was assessed using the Strategies for Pronunciation Improvement (SPI) Inventory (Sardegna et al., 2018). The expected evidence of cross-linguistic interference was not found, and phonetic awareness did not serve to modulate the degree of cross-linguistic interference. The discussion considers whether the lack of convergence in the code-switching context may result from both sociolinguistic and cognitive factors and discusses how this finding can affect the exploration of phonetic awareness in cross-linguistic interference.</p>

<p dir="ltr">Suprasegmental features (i.e., features realized through pitch, volume, and/or duration changes) are particularly difficult for second language learners. This has led to the creation of many different methods of training, often employing the use of experimenter or instructor-created training materials. However, the use of authentic materials for training suprasegmental features remains underexplored. Authentic materials have recently been shown to be useful for some aspects of language learning, such as communicative competence and listening comprehension, while their usefulness for training suprasegmental features remains unclear.</p><p dir="ltr">This dissertation explores the potential usefulness of authentic materials for training two suprasegmental features, second language (L2) lexical tone in Mandarin and L2 lexical pitch accent in Japanese. For each language, participants were divided into an authentic group and an inauthentic group based on the type of materials they were exposed to during a shadowing task. Participants then used words they shadowed in a visual feedback task, which was chosen due to visual feedback’s previously proven usefulness for training these two features.</p><p dir="ltr">For each language, L2 productions at the pretest, posttest, and delayed posttest were compared to first language (L1) productions using a previously established analysis known as the <i>CID </i>measure analysis. The resulting time-series plots, <i>CID </i>measures, magnitudes (pitch height), and phases (timing), were analyzed to determine which group, authentic or inauthentic, performed in a more L1-like way at the posttest compared to the pretest. Results suggest that the authentic group outperformed the inauthentic group for three out of four Mandarin tones, and three out of seven Japanese pitch accent patterns. These results begin to show support for the usefulness of authentic materials, with experimental and pedagogical implications for researchers and learners of Mandarin and Japanese.</p>

One of the key features of the hypokinetic dysarthria associated with Parkinson disease is dysprosody. While there has been ample research into the global characterization of speech in Parkinson disease, little is known about how people with Parkinson disease mark lexical stress. This study aimed to determine how people with Parkinson disease modulate pitch, intensity, duration, and vowel space to differentiate between two common lexical stress patterns in English: trochees (strong-weak pattern) and iambs (weak-strong pattern), in two syllable words. Twelve participants with mild to moderate idiopathic Parkinson disease and twelve age- and sex-matched controls completed a series of speech tasks designed to elicit token words of interest in prosodically-relevant speech tasks (picture identification (in isolation and lists) and giving directions (spontaneous speech). Results revealed that people with Parkinson disease produced a higher overall pitch and a smaller vowel space as compared to controls, though most lexical marking features were not significantly different. Importantly, the elicitation task had a significant effect on most dependent measures. Although lexical stress is not significantly impacted by Parkinson disease, we recommend that future research and clinical practice focus more on the use of spontaneous speech tasks rather than isolated words or lists of words due to the differences in the marking of lexical stress in the latter tasks, making them less useful as ecologically-valid assessments of prosody in everyday communication.

<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>

<p dir="ltr">The present dissertation addresses the gap of how the three contextual variables (power, distance, and imposition) affect the use and perception of pitch range and final pitch contours in Central Peninsular Spanish polar questions. The methodological approach in this dissertation combines a production experiment in the form of a contextualized sentence-reading task (e.g., Brown et al., 2014; Henriksen, 2013) and a perception experiment using a pragmatic judgment task (e.g., Nadeu & Prieto, 2011). Both tasks systematically incorporated a set of situations that included the contextual variables of power, distance, and imposition. Thus, this dissertation provides a systematic analysis of power, distance, and imposition to investigate their influence on the use and perception of pitch range and pitch contours. To analyze pitch in the production experiment, a categorical analysis of final pitch contours (e.g., low-rising contour) and a quantitative analysis of prosodic features (i.e., pitch range and its conversion into semitones) were conducted. For the perception experiment, analyses included the comparison of linear mixed models to examine the perceived degree of politeness.</p><p dir="ltr">The findings presented in this dissertation support the Frequency Code Hypothesis in that they showed the relevance of pitch for signaling and perceiving politeness in requests in Spanish. The results from the production experiment suggested there are no effects of power, distance, and imposition on the selection of final intonational contours. Regarding the analysis of pitch range, the results from the production experiment indicated that the use of greater pitch range was associated with an increase in the social distance between the speakers. In the perception experiment, the results indicated that an increase in pitch range was directly associated with an increase in the perceived degree of politeness. Furthermore, the findings from this dissertation provided evidence for including a systematic analysis of the contextual variables of power, distance, and imposition to conduct analyses within the politeness framework instead of analyzing the formal/informal dimension in isolation The overall results of this dissertation contribute to the understanding of how suprasegmental features are employed in showing and perceivicing politeness.</p>