6 research outputs found

    Prosodic structural effects on coarticulatory vowel nasalization in Australian English in comparison to American English

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    This study investigates effects of prosodic factors (prominence, boundary) on coarticulatory Vnasalization in Australian English (AusE) in CVN and NVC in comparison to those in American English (AmE). As in AmE, prominence was found to lengthen N, but to reduce V-nasalization, enhancing N’s nasality and V’s orality, respectively (paradigmatic contrast enhancement). But the prominence effect in CVN was more robust than that in AmE. Again similar to findings in AmE, boundary induced a reduction of N-duration and V-nasalization phrase-initially (syntagmatic contrast enhancement), and increased the nasality of both C and V phrasefinally. But AusE showed some differences in terms of the magnitude of V nasalization and N duration. The results suggest that the linguistic contrast enhancements underlie prosodic-structure modulation of coarticulatory V-nasalization in comparable ways across dialects, while the fine phonetic detail indicates that the phonetics-prosody interplay is internalized in the individual dialect’s phonetic grammar

    Planting the seed for sound change: Evidence from real-time MRI of velum kinematics in German

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    Velum movement signals generated from real-time magnetic resonance imaging videos of thirty-five German speakers were used to investigate the physiological conditions that might promote sound change involving the development of contrastive vowel nasality. The results suggest that, in comparison to when a nasal consonant precedes a voiced obstruent, the velum gesture associated with a nasal consonant preceding a voiceless obstruent undergoes gestural rescaling and temporal rephasing. This further suggests that the diachronic development of contrastive vowel nasality comprises two stages: the first stage involves gestural shortening and realignment, while the second stage involves a trading relationship between source and effect

    Planting the seed of sound change: Evidence from real-time MRI of velum kinematics in German

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    Velum movement signals generated from real-time magnetic resonance imaging videos of thirty-five German speakers were used to investigate the physiological conditions that might pro-mote sound change involving the development of contrastive vowel nasality. The results suggest that, in comparison to when a nasal consonant precedes a voiced obstruent, the velum gesture as-sociated with a nasal consonant preceding a voiceless obstruent undergoes gestural rescaling and temporal rephasing. This further suggests that the diachronic development of contrastive vowel nasality comprises two stages: the first stage involves gestural shortening and realignment, while the second stage involves a trading relationship between source and effect

    Analyzing speech in both time and space : generalized additive mixed models can uncover systematic patterns of variation in vocal tract shape in real-time MRI

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    We present a method of using generalized additive mixed models (GAMMs) to analyze midsagittal vocal tract data obtained from real-time magnetic resonance imaging (rt-MRI) video of speech production. Applied to rt-MRI data, GAMMs allow for observation of factor effects on vocal tract shape throughout two key dimensions: time (vocal tract change over the temporal course of a speech segment) and space (location of change within the vocal tract). Examples of this method are provided for rt-MRI data collected at a temporal resolution of 20 ms and a spatial resolution of 1.41 mm, for 36 native speakers of German. The rt-MRI data were quantified as 28-point semi-polar-grid aperture functions. Three test cases are provided as a way of observing vocal tract differences between: (1) /aː/ and /iː/, (2) /aː/ and /aɪ/, and (3) accentuated and unstressed /aː/. The results for each GAMM are independently validated using functional linear mixed models (FLMMs) constructed from data obtained at 20% and 80% of the vowel interval. In each case, the two methods yield similar results. In light of the method similarities, we propose that GAMMs are a robust, powerful, and interpretable method of simultaneously analyzing both temporal and spatial effects in rt-MRI video of speech

    Spontaneous nasalization: An articulatory investigation of glottal consonants in Thai

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    Vowel nasalization usually occurs through a two-step process whereby a vowel is nasalized via coarticulation with a nearby nasal segment; when the language later drops the nasal segment, a nasal vowel remains. Spontaneous vowel nasalization is a rare, peculiar form of nasalization that emerges in contexts that lack an historical etymological nasal (Blevins and Garrett, 1992; Matisoff, 1975; Ohala, 1975, 1974). Spontaneous vowel nasalization has been found to emerge in contexts with glottal consonants, low vowels, and transitionally breathy segments such as fricatives and aspirates. Blevins and Garrett (1992) classified these contexts as rhinoglottophilia ‘nose-larynx-affinity’, rhinochthamalophilia ‘nose-low/flat-affinity’, and rhinosyrigmatophilia ‘nose-whistle-affinity’. Many articulatory and acoustic explanations have been proposed for spontaneous nasalization. First, vowels may nasalize near glottal consonants because they are underspecified for velopharyngeal opening and thus may be produced with a lowered velum. Second, low vowels may nasalize because they can better tolerate the acoustic consequences of greater nasal coupling; the intraoral acoustic impedance of low vowels is naturally lower. Finally, speakers may nasalize vowels in breathy environments through misperception or enhancement because nasality and breathiness are acoustically similar (Matisoff, 1975; Ohala and Amador, 1981). Due to the acoustic similarities between nasalization and breathiness, e.g. high spectral tilt and weakened F1, disentangling the relative roles of physiological nasalization and breathiness during spontaneous nasalization is not possible using acoustic data alone. There have been few articulatory investigations that assess the origins of spontaneous nasalization (Clumeck, 1975; Ohala, 1971). Thai arguably manifests an interaction among rhinoglottophilia, rhinochthamalophilia, and rhinosyrigmatophilia-based spontaneous nasalization. Thai is known to nasalize low and mid-low vowels after the voiceless glottal fricative /h/ and glottal stop /ʔ/, such that /hɛ˨/ [hɛ̃˨] ‘parade’ and /ʔaw˧/ [ʔãw˧] ‘to take’ are reported to sound nasal (Cooke, 1989; Matisoff, 1975; Noss, 1964). Vowels following /h/ are reportedly more susceptible to nasalization than those following /ʔ/ (Matisoff, 1975; Cooke, 1989). Furthermore, of the nasalized vowels, Cooke (1989) observed that /a/ is reported to sound more nasal than /ɛ/ and /ɔ/. In Thai it is possible that the velopharyngeal underspecification of glottal consonants, low tongue height, and breathy-nasal acoustic similarity (in proximity to /h/) may all play a role in nasalization. In order to deepen our understanding of these potentially interacting sources of spontaneous nasalization in Thai, this dissertation undertakes an extensive articulatory investigation of physiological nasalization and breathiness during spontaneously nasalized vowels in Central Thai. Spontaneous nasalization has been an historically difficult topic of study because its analysis requires a combination of articulatory data that measures both nasalization and phonation quality. This dissertation integrates measures from state-of-the-art ultra-fast magnetic resonance imaging (MRI), aerodynamics, and electroglottography (EGG) to estimate physiological nasalization and breathiness. The speech of ten speakers of Central Thai was assessed using these tools: Four speakers were recorded using ultra-fast MRI and six speakers were recorded using aerodynamics and EGG. Speakers produced CV syllables that varied by onset consonant and vowel height within the same carrier phrase. Syllables with an onset glottal consonant /h, ʔ/ were varied at four different vowel heights; syllables with onset consonants /n, th, d/ were included as nasal and oral controls. The major finding of this dissertation is that /h/-onset syllables are produced with greater physiological nasalization than /ʔ/-onset syllables. This finding suggests that, counter to previous claims that glottal consonants are generally underspecified for velopharyngeal opening in Thai, /ʔ/ is in fact specified, at least in a prosodically prominent context. Furthermore, using EGG we observed a slight increase in breathiness during vowels just after /h/, but not after /ʔ/, suggesting a potential relationship between nasalization and breathiness in Thai. The voiceless turbulence of /h/ induces coarticulatory breathiness during the following vowel; this breathiness may facilitate the perception of nasalization during the following vowel. This might explain why vowels after /h/ reportedly sound more nasal than vowels after /ʔ/ (Cooke, 1989; Matisoff, 1975). Further perceptual testing is needed to assess this possibility. Furthermore, we observed inconsistent and often minimal variation in physiological nasalization during vowels of varying height in both nasalized and non-nasal context. This suggests that spontaneous vowel nasalization in Central Thai may now be similar to Northeastern Thai, a dialect where all vowels were reported to nasalize after glottal consonants approximately 40 years ago (Matisoff, 1975). Finally, during /hV/ syllables, all /h/ consonants are produced with greater nasal airflow than the following vowel. The onset /h/ appears to be the locus of nasalization that spreads to the vowel through coarticulation. The results of this dissertation deepen our understanding of the production of spontaneous nasalization and contexts that facilitate its realization in Thai and perhaps crosslinguistically as well. Our results demonstrate that spontaneous nasalization in Thai is primarily attributed to rhinoglottophilia: velopharyngeal underspecification of onset /h/. Rhinosyrigmatophilia may potentially also play a role: the presence of breathiness after /h/ may enhance the percept of nasalization. Nasal coupling and breathiness may be integrated into a single acoustic object that the listener perceives as nasal. This possibility presents an intriguing example of the many-to-one problem, whereby many possible articulatory configurations may result in similar acoustic output (Maeda, 1990)
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