The use of acoustic cues in phonetic perception: Effects of spectral degradation, limited bandwidth and background noise

Hearing impairment, cochlear implantation, background noise and other auditory degradations result in the loss or distortion of sound information thought to be critical to speech perception. In many cases, listeners can still identify speech sounds despite degradations, but understanding of how this is accomplished is incomplete. Experiments presented here tested the hypothesis that listeners would utilize acoustic-phonetic cues differently if one or more cues were degraded by hearing impairment or simulated hearing impairment. Results supported this hypothesis for various listening conditions that are directly relevant for clinical populations. Analysis included mixed-effects logistic modeling of contributions of individual acoustic cues for various contrasts. Listeners with cochlear implants (CIs) or normal-hearing (NH) listeners in CI simulations showed increased use of acoustic cues in the temporal domain and decreased use of cues in the spectral domain for the tense/lax vowel contrast and the word-final fricative voicing contrast. For the word-initial stop voicing contrast, NH listeners made less use of voice-onset time and greater use of voice pitch in conditions that simulated high-frequency hearing impairment and/or masking noise; influence of these cues was further modulated by consonant place of articulation. A pair of experiments measured phonetic context effects for the "s/sh" contrast, replicating previously observed effects for NH listeners and generalizing them to CI listeners as well, despite known deficiencies in spectral resolution for CI listeners. For NH listeners in CI simulations, these context effects were absent or negligible. Audio-visual delivery of this experiment revealed enhanced influence of visual lip-rounding cues for CI listeners and NH listeners in CI simulations. Additionally, CI listeners demonstrated that visual cues to gender influence phonetic perception in a manner consistent with gender-related voice acoustics. All of these results suggest that listeners are able to accommodate challenging listening situations by capitalizing on the natural (multimodal) covariance in speech signals. Additionally, these results imply that there are potential differences in speech perception by NH listeners and listeners with hearing impairment that would be overlooked by traditional word recognition or consonant confusion matrix analysis

Perception and Acquisition of Natural Authentic English Speech for Chinese Learners Using DIT\u27s Speech Technologies

Given that Chinese language learners are greatly influenced by their mother-tongue, which is a tone language rather than an intonation language, learning and coping with authentic English speech seems more difficult than for learners of other languages. The focus of the current research is, on the basis of analysis of the nature of spoken English and spoken Chinese, to help Chinese learners derive benefit from ICT technologies developed by the Technological University Dublin (DIT). The thesis concentrates on investigating the application of speech technologies in bridging the gap between students’ internalised, idealised formulations and natural, authentic English speech. Part of the testing carried out by the present author demonstrates the acceptability of a slow-down algorithm in facilitating Chinese learners of English in re-producing formulaic language. This algorithm is useful because it can slow down audio files to any desired speed between 100% and 40% without distortion, so as to allow language learners to pay attention to the real, rapid flow of ‘messy’ speech and follow the intonation patterns contained in them. The rationale for and the application of natural, dialogic native-to-native English speech to language learning is also explored. The Chinese language learners involved in this study are exposed to authentic, native speech patterns by providing them access to real, informal dialogue in various contexts. In the course of this analysis, the influence of speed of delivery and pitch range on the categorisation of formulaic language is also investigated. The study investigates the potential of the speech tools available to the present author as an effective EFL learning facility, especially for speakers of tone languages, and their role in helping language learners achieve confluent interaction in an English L1 environment

Mechanism of extreme phonetic reduction: evidence from Taiwan Mandarin

Extreme reduction refers to the phenomenon where intervocalic consonants are so severely reduced that two or more adjacent syllables appear to be merged into one. Such severe reduction is often considered a characteristic of natural speech and to be closely related to factors including lexical frequency, information load, social context and speaking style. This thesis takes a novel approach to investigating this phenomenon by testing the time pressure account of phonetic reduction, according to which time pressure is the direct cause of extreme reduction. The investigation was done with data from Taiwan Mandarin, a language where extreme reduction (referred to as contraction) has been reported to frequently occur. Three studies were conducted to test the main hypothesis. In Study 1, native Taiwan Mandarin speakers produced sentences containing nonsense disyllabic words with varying phonetic structures at differing speech rates. Spectral analysis showed that extreme reduction occurred frequently in nonsense words produced under high time pressure. In Study 2a, further examination of formant peak velocity as a function of formant movement amplitude in experimental data suggested that articulatory effort was not decreased during reduction, but in fact likely to be increased. Study 2b examined high frequency words from three spontaneous speech corpora for reduction variations. Results demonstrate that patterns of reduction in high frequency words in spontaneous speech (Study 2b) were similar to those in nonsense words spoken under experimental conditions (Study 2a). Study 3 investigated tonal reduction with varying tonal contexts and found that tonal reduction can also be explained in terms of time pressure. Analysis of F0 trajectories demonstrates that speakers attempt to reach the original underlying tonal targets even in the case of extreme reduction and that there was no weakening of articulatory effort despite the severe reduction. To further test the main hypothesis, two computational modelling experiments were conducted. The first applied the quantitative Target Approximation model (qTA) for tone and intonation and the second applied the Functional Linear Model (FLM). Results showed that severely reduced F0 trajectories in tone dyads can be regenerated to a high accuracy by qTA using generalized canonical tonal targets with only the syllable duration modified. Additionally, it was shown that using FLM and adjusting duration alone can give a fairly good representation of contracted F0 trajectory shapes. In summary, results suggest that target undershoot under time pressure is likely to be the direct mechanism of extreme reduction, and factors that have been commonly associated with reduction in previous research very likely have an impact on duration, which in turn determines the degree of target attainment through the time pressure mechanism

Do Irrelevant Sounds Impair the Maintenance of All Characteristics of Speech in Memory?

Several studies have shown that maintaining in memory some attributes of speech, such as the content or pitch of an interlocutor's message, is markedly reduced in the presence of background sounds made of spectrotemporal variations. However, experimental paradigms showing this interference have only focused on one attribute of speech at a time, and thus differ from real-life situations in which several attributes have to be memorized and maintained simultaneously. It is possible that the interference is even greater in such a case and can occur for a broader range of background sounds. We developed a paradigm in which participants had to maintain the content, pitch and speaker size of auditorily presented speech information and used various auditory distractors to generate interference. We found that only distractors with spectrotemporal variations impaired the detection, which shows that similar interference mechanisms occur whether there are one or more speech attributes to maintain in memory. A high percentage of false alarms was observed with these distractors, suggesting that spectrotemporal variations not only weaken but also modify the information maintained in memory. Lastly, we found that participants were unaware of the interference. These results are similar to those observed in the visual modalit

Teaching pronunciation:a case for a pedagogy based upon intelligibility

This thesis examines the main aim of teaching pronunciation in second language acquisition in the Syrian context. In other words, it investigates the desirable end point, namely: whether it is native-like accent, or intelligible pronunciation. This thesis also investigates the factors that affect native-like pronunciation and intelligible accent. It also analyses English language teaching methods. The currently used English pronunciation course is examined in detail too. The aim is to find out the learners’ aim of pronunciation, the best teaching method for achieving that aim, and the most appropriate course book that fulfils the aim. In order to find out learners’ aim in pronunciation, a qualitative research is undertaken. The research takes advantage of some aspects of case study. It is also supported by a questionnaire to gather data. The result of this research can be regarded as an attempt to bring the Syrian context to the current trends in the teaching of English pronunciation. The results show that learners are satisfied with intelligible pronunciation. The currently used teaching method (grammar-translation method) may be better replaced by the (communicative approach) which is more appropriate than the currently used method. It is also more effective to change the currently used book to a new one that corresponds to that aim. The current theories and issues in teaching English pronunciation that support learners’ intelligibility will be taken into account in the newly proposed course book

Enhancing the pronunciation of problematic English consonants for Spanish learners through intralingual dubbing activities

En esta tesis doctoral se proporciona un estudio sobre el potencial de las actividades de doblaje intralingüístico en la mejora de la pronunciación de fonemas consonánticos problemáticos del inglés para estudiantes españoles, junto con otras consideraciones adicionales, como el grado en que esos fonemas resultan problemáticos para los participantes de la investigación (n=71) y un análisis pormenorizado de sus puntos de vista y opiniones sobre la actividad de doblaje.Para ello, un Grupo Experimental (GE; n=37) y un Grupo Control (GC; n=34) se grabaron en diferentes fases del estudio (GE: fase pre-test, doblajes, y fase post-test; GC: pre-test y post-test) con el fin de obtener datos relevantes y útiles sobre su pronunciación. Todos los datos recopilados han sido analizados con el Statistical Package for Social Sciences, (SPSS; v.25), aplicando el test de Wilcoxon para comparaciones intragrupales, y el U-test de Mann-Whitney para las comparaciones entre grupos. Además, los participantes de la investigación completaron dos cuestionarios para obtener información adicional al respecto.Como conclusión, la pronunciación general del GE mejoró significativamente en la mayoría de los fonemas consonánticos problemáticos durante y después de realizar las actividades de doblaje, mientras que el GC no mostró ninguna mejora significativa en su pronunciación. Además, la mayoría de los participantes del GE mostraron opiniones muy positivas hacia la actividad de doblaje, destacando su valor motivador e innovador en el aprendizaje de lenguas, así como su utilidad para mejorar las habilidades orales.<br /

Influence of ear canal occlusion and air-conduction feedback on speech production in noise

Millions of workers are exposed to high noise levels on a daily basis. The primary concern for these individuals is the prevention of noise-induced hearing loss, which is typically accomplished by wearing of some type of personal hearing protector. However, many workers complain they cannot adequately hear their co-workers when hearing protectors are worn. There are many aspects related to fully understanding verbal communication between noise-exposed workers that are wearing hearing protection. One topic that has received limited attention is the overall voice level a person uses to communicate in a noisy environment. Quantifying this component provides a starting point for understanding how communication may be improved in such situations. While blocking out external sounds, hearing protectors also induce changes in the wearer’s self-perception of his/her own voice, which is known as the occlusion effect. The occlusion effect and attenuation provided by hearing protectors generally produce opposite effects on that individual’s vocal output. A controlled laboratory study was devised to systematically examine the effect on a talker’s voice level caused by wearing a hearing protector and while being subjected to high noise levels. To test whether differences between occluded and unoccluded vocal characteristics are due solely to the occlusion effect, speech produced while subjects’ ear canals were occluded was measured without the subject effectively receiving any attenuation from the hearing protectors. To test whether vocal output differences are due to the reduction in the talker’s self-perceived voice level, the amount of occlusion was held constant while varying the effective hearing protector attenuation. Results show the occlusion effect, hearing protector attenuation, and ambient noise level all to have an effect on the talker’s voice output level, and all three must be known to fully understand and/or predict the effect in a particular situation. The results of this study may be used to begin an effort to quantify metrics in addition to the basic noise reduction rating that may be used to evaluate a hearing protector’s practical usability/wearability. By developing such performance metrics, workers will have information to make informed decisions about which hearing protector they should use for their particular work environment