Structured heterogeneity in Scottish stops over the 20th Century

How and why speakers differ in the phonetic implementation of phonological contrasts, and the relationship of this ‘structured heterogeneity’ to language change, has been a key focus over fifty years of variationist sociolinguistics. In phonetics, interest has recently grown in uncovering ‘structured variability’—how speakers can differ greatly in phonetic realization in nonrandom ways—as part of the long-standing goal of understanding variability in speech. The English stop voicing contrast, which combines extensive phonetic variability with phonological stability, provides an ideal setting for an approach to understanding structured variation in the sounds of a community’s language that illuminates both synchrony and diachrony. This article examines the voicing contrast in a vernacular dialect (Glasgow Scots) in spontaneous speech, focusing on individual speaker variability within and across cues, including over time. Speakers differ greatly in the use of each of three phonetic cues to the contrast, while reliably using each one to differentiate voiced and voiceless stops. Interspeaker variability is highly structured: speakers lie along a continuum of use of each cue, as well as correlated use of two cues—voice onset time and closure voicing—along a single axis. Diachronic change occurs along this axis, toward a more aspiration-based and less voicing-based phonetic realization of the contrast, suggesting an important connection between synchronic and diachronic speaker variation

Structured Speaker Variability in Spontaneous Japanese Stop Contrast Production

Studies of speaker variability in the realisation of stop voicing contrasts have demonstrated that differences across speakers are highly structured both within and across phonetic categories. These studies have focused on languages with similar voicing systems in scripted speech; it remains unclear how stop realisation varies in spontaneous speech more generally. This study examines speaker variability in two acoustic cues to stop voicing–Voice Onset Time and Voicing During Closure–in a corpus of spontaneous Japanese, a language undergoing change in its voicing contrast. Whilst speakers vary in both measures, this variability is highly structured: speakers with less aspirated stops are more likely to initiate voicing during the closure. However, no corresponding relationship is observed between how the two cues are used to mark the contrast. These findings extend previous work to demonstrate the structure of speaker variability in spontaneous speech

Effects of Phonological Contrast on Within-Category Phonetic Variation

This dissertation investigates an often assumed hypothesis in phonetics and phonology: that there should be relatively less within-category phonetic variation in production in languages which have relatively more phonological contrasts (Lindblom, 1986, on vowels). Although this hypothesis is intuitive, there is little existing evidence to support the claim and it is difficult to generalize outside of vowels. In this dissertation, I argue that this hypothesis is not trivially true and needs additional specification. I propose an extension of this hypothesis, Contrast-Dependent Variation, which predicts relative differences in extent of within-category variation between languages and individual speakers. Contrast-Dependent Variation can make predictions across multiple phonetic spaces as it considers individual phonetic dimensions to be the relevant units of comparison, rather than phonological inventory subsets (stops, vowels, etc.). Relative differences in extent of within-category variation are predicted by differences in cue weight, rather than differences in number of phonemes. The dissertation tests this hypothesis by examining two between-language case studies: stops in Hindi and English and sibilants in French and Polish. I also consider a within-language case study: individual differences in extent of within-category variation in Mandarin sibilants. The results here show that differences in extent of phonetic variability between languages and speakers are systematic; they are structured according to the system of phonological contrasts

The role of experience in processing foreign-accented speech

The present study examines the perceptual accommodation of the bilabial stop-consonant voicing contrast (i.e., /b/ vs. /p/), in several English- and Spanish-accented contexts, by native Spanish listeners with different degrees of experience with accented speech. In a series of four experiments, we confronted three potential mechanisms for the perceptual accommodation of foreign-accented sounds. According to the first mechanism (phonetic relaxation), listeners accommodate foreign-accented sounds by relaxing the phonetic boundary between native speech sound categories. According to the second mechanism (phonetic calibration), listeners accommodate foreign-accented sounds by adjusting the location of native perceptual boundaries according to the phonetic realization of native categories in the foreign-accented speech context. Finally, according to the third mechanism (phonetic switching), foreign-accented speech sounds are accommodated by switching to a non-native system of phonetic representations that was previously developed through long-term experience with the speech norm of the foreign accent. Experimental results indicate that Spanish listeners did not relax the phonetic boundary between /b/ and /p/ in an English-accented Spanish context (Experiments 1 and 3). However, they accommodated English-accented Spanish voicing differently, depending on their degree of experience with the English-accented speech norm. When Spanish listeners had little or no experience with the English norm, they calibrated the location of the perceptual boundary between /b/ and /p/ according to the Spanish or English phonetic realization of these sounds in the speech context (Experiment 4). Alternatively, when they had a high degree of experience with English-accented speech, they accommodated English-accented Spanish /b/ and /p/ by using an English-like system of phonetic representations that was not predictable from the phonetic realization of /b/ and /p/ in the speech context (Experiments 1 and 2). These experimental results contribute to a better understanding of the role played by non-native experience in the perceptual accommodation of foreign-accents. In particular, they indicate that native listeners may rely on previous long-term experience with the native language of the foreign-accented speaker to efficiently accommodate foreign-accented speech variability in a different way to which they accommodate speech variability from different native-accented speakers

Structured heterogeneity in Scottish stops over the twentieth 20th century

How and why speakers differ in the phonetic implementation of phonological contrasts, and the relationship of this ‘structured heterogeneity’ to language change, has been a key focus over 50 years of variationist sociolinguistics. In phonetics, interest has recently grown in uncovering ‘structured variability’—how speakers can differ greatly in phonetic realization in non-random ways—as part of the longstanding goal of understanding variability in speech. The English stop voicing contrast, which combines extensive phonetic variability with phonological stability, provides an ideal setting for an approach to understanding structured variation in the sounds of a community’s language which illuminates both synchrony and diachrony. This paper examines the voicing contrast in a vernacular dialect (Glasgow Scots) in spontaneous speech, focusing on individual speaker variability within and across cues, including over time. Speakers differ greatly in the use of each of three phonetic cues to the contrast, while reliably using each one to differentiate voiced and voiceless stops. Interspeaker variability is highly structured: speakers lie along a continuum of use of each cue, as well as correlated use of two cues—VOT and closure voicing—along a single axis. Diachronic change occurs along this axis, towards a more aspiration-based and less voicing-based phonetic realization of the contrast, suggesting an important connection between synchronic and diachronic speaker variation

Acoustic-phonetic and auditory mechanisms of adaptation in the perception of sibilant fricatives

Listeners are highly proficient at adapting to contextual variation when perceiving speech. In the present study, we examined the effects of brief speech and nonspeech contexts on the perception of sibilant fricatives. We explored three theoretically motivated accounts of contextual adaptation, based on phonetic cue calibration, phonetic covariation, and auditory contrast. Under the cue calibration account, listeners adapt by estimating a talker-specific average for each phonetic cue or dimension; under the cue covariation account, listeners adapt by exploiting consistencies in how the realization of speech sounds varies across talkers; under the auditory contrast account, adaptation results from (partial) masking of spectral components that are shared by adjacent stimuli. The spectral center of gravity, a phonetic cue to fricative identity, was manipulated for several types of context sound: /z/-initial syllables, /v/-initial syllables, and white noise matched in long-term average spectrum (LTAS) to the /z/-initial stimuli. Listeners’ perception of the /s/–/ʃ/ contrast was significantly influenced by /z/-initial syllables and LTAS-matched white noise stimuli, but not by /v/-initial syllables. No significant difference in adaptation was observed between exposure to /z/-initial syllables and matched white noise stimuli, and speech did not have a considerable advantage over noise when the two were presented consecutively within a context. The pattern of findings is most consistent with the auditory contrast account of short-term perceptual adaptation. The cue covariation account makes accurate predictions for speech contexts, but not for nonspeech contexts or for the absence of a speech-versus-nonspeech difference

Structured speaker variability in Japanese stops: relationships within versus across cues to stop voicing

A number of recent studies have observed that phonetic variability is constrained across speakers, where speakers exhibit limited variation in the signalling of phonological contrasts in spite of overall differences between speakers. This previous work focused predominantly on controlled laboratory speech and on contrasts in English and German, leaving unclear how such speaker variability is structured in spontaneous speech and in phonological contrasts that make substantial use of more than one acoustic cue. This study attempts to both address these empirical gaps and expand the empirical scope of research investigating structured variability by examining how speakers vary in the use of positive voice onset time and voicing during closure in marking the stop voicing contrast in Japanese spontaneous speech. Strong covarying relationships within each cue across speakers are observed, while between-cue relationships across speakers are much weaker, suggesting that structured variability is constrained by the language-specific phonetic implementation of linguistic contrasts

The Online Adjustment Of Speaker-Specific Phonetic Beliefs In Multi-Speaker Speech Perception

This dissertation examines how listeners\u27 knowledge of interspeaker variability guides their generalization of perceptual learning in multi-talker listening. A series of perceptual learning experiments are conducted to evaluate whether listeners generalize what they have learned about a previous talker\u27s production of sibilants and stop VOT to another speaker either of the same gender or a different gender. Experiment 1 and 2 finds that the perceptual learning of sibilants constantly generalizes across speakers of different genders under an acoustics-phonology mismatch constraint. The constraint states that perceptual learning fails to generalize if there is a mismatch between the directions of perceptual shifts intended by the raw acoustic distributions of stimuli and by their phonological distribution in the perceptual space. Experiment 3 reports evidence for the perceptual generalization of stop VOT across speakers of different genders. These results lend support to a cumulative update account, which suggests that perceptual learning updates across speakers in such a way where previous and current perceptual learning experiences are re-integrated to form a cumulative perceptual expectation that listeners use for upcoming perception events. Building on the above findings, Experiment 4 investigates the constraints of speaker identity and gender on the perceptual generalization of sibilants and stops by introducing and manipulating visual identity and voice gender cues. The results show reduced magnitude for perceptual generalization across genders than within gender, and, in the latter case, for perceptual generalization across speakers than within speaker. These results raise the possibility that socioindexical specificity imposes a constraint on perceptual learning by modulating the magnitude of perceptual generalization across social groups, instead of blocking its occurrence. They also suggest that listeners\u27 knowledge of structure in talker variability may be more fine-grained than hard-and-fast bindings of social-demographic groups and lend support to the sophisticated interweaving of social information in the architecture of the phonetics-phonological mapping system

Voice Onset Time Enhanced User System (VOTEUS): a web graphic interface for the analysis of plosives’ release phases

The paper proposes an up-to-date literature review of the works using AutoVOT, a discriminative large-margin learning algorithm developed for the semi-automatic measurement of voice onset times. In order to expand the accessibility of the tool in linguistic research, we present VOTEUS, a user-friendly graphic interface written in Python. The interface is conceived to assist the researcher throughout the whole process of annotation, from the forced alignment of the corpora to the refinement of the AutoVOT tier and the extraction of the durations. The general aim is to speed up this phase of data analysis, providing a significant improvement on prevalent practice to date