Hiatus resolution and linguistic diversity in Australian English.

Vowel hiatus is typically resolved in Australian English through complementary strategies of liaison (j-gliding/w-gliding/linking-r) and glottalisation. Previous work suggests a change in progress towards increased use of glottalisation as an optimal hiatus-breaker, which creates syntagmatic contrast between adjacent vowels, particularly when the right-edge vowel is strong (i.e. at the foot boundary). Liaison continues to be used when right-edge vowels are weak, but glottalisation as a hiatus resolution strategy in general appears to be increasing and may be more common in speakers from non-English speaking backgrounds raising the question of whether exposure to linguistic diversity could be driving the change. We examine hiatus resolution in speakers from neighbourhoods that vary according to levels of language diversity. We elicited gliding and linking-r hiatus contexts to determine how prosodic strength of flanking vowels and speakers' exposure to linguistic diversity affect hiatus resolution. Results confirm that glottalisation occurs most frequently with strong right-edge vowels, and gliding/linking-r are more likely with weak right-edge vowels. However, strategies differ between gliding and linking-r contexts, suggesting differing implementation mechanisms. In addition, speakers from ethnolinguistically diverse areas produce increased glottalisation in all contexts supporting the idea that change to the hiatus resolution system may be driven by language contact.

Reconsidering lateral vocalisation: Evidence from perception and production of Australian English /l/.

Lateral vocalisation is assumed to arise from changes in coronal articulation but is typically characterised perceptually without linking the vocalised percept to a coronal articulation. Therefore, we examined how listeners' perception of coda /l/ as vocalised relates to coronal closure. Perceptual stimuli were acquired by recording laterals produced by six speakers of Australian English using electromagnetic articulography (EMA). Tongue tip closure was monitored for each lateral in the EMA data. Increased incidence of incomplete coronal closure was found in coda /l/ relative to onset /l/. Having verified that the dataset included /l/ tokens produced with incomplete coronal closure-a primary articulatory cue of vocalised /l/-we conducted a perception study in which four highly experienced auditors rated each coda /l/ token from vocalised (3) to non-vocalised (0). An ordinal mixed model showed that increased tongue tip (TT) aperture and delay correlated with vocalised percept, but auditors ratings were characterised by a lack of inter-rater reliability. While the correlation between increased TT aperture, delay, and vocalised percept shows that there is some reliability in auditory classification, variation between auditors suggests that listeners may be sensitive to different sets of cues associated with lateral vocalisation that are not yet entirely understood.

Evaluating automatic creaky voice detection methods.

There is growing interest in research on the non-modal voice quality, creaky voice; however, its identification often relies on time-consuming manual annotation, leading to a recent focus on automatic creak detection methods. Various automatic methods have been proposed, which rely on varying types and combinations of acoustic cues for creak detection. In this paper, we compare the performance of three automatic tools, the AntiMode method, the Creak Detector algorithm, and the Roughness algorithm, against manual annotation of creak using data from 80 Australian English speakers. We explore the possibility that tools used in combination may yield more accurate creak detection than individual tools used alone. Based on method comparisons, we present options for researchers, including an "out-of-the-box" approach, which supports combining automatic tools, and propose additional steps to further improve creak detection. We found restricting analysis to sonorant segments significantly improves automatic creak detection, and tools performed consistently better on female speech than male speech. Findings support previous work showing detection may be optimised by performing a creak probability threshold sweep on a subset of data prior to applying the Creak Detector algorithm on new datasets. Results provide promising solutions for advancing efficient large-scale research on creaky voice.

Spectral contrast reduction in Australian English /l/-final rimes.

Vowel contrasts may be reduced or neutralized before coda laterals in English [Bernard (1985). The Cultivated Australian: Festschrift in Honour of Arthur Delbridge, pp. 319-332; Labov, Ash, and Boberg (2008). The Atlas of North American English, Phonetics and Sound Change (Gruyter Mouton, Berlin); Palethorpe and Cox (2003). International Seminar on Speech Production (Macquaire University, Sydney, Australia)], but the acoustic characteristics of vowel-lateral interaction in Australian English (AusE) rimes have not been systematically examined. Spectral and temporal properties of 16 pre-lateral and 16 pre-obstruent vowels produced by 29 speakers of AusE were compared. Acoustic vowel similarity in both environments was captured using random forest classification and hierarchical cluster analysis of the first three DCT coefficients of F1, F2, and F3, and duration values. Vowels preceding /l/ codas showed overall increased confusability compared to vowels preceding /d/ codas. In particular, reduced spectral contrast was found for the rime pairs /iːl-ɪl/ (feel-fill), /ʉːl-ʊl/ (fool-full), /əʉl-ɔl/ (dole-doll), and /æɔl-æl/ (howl-Hal). Potential articulatory explanations and implications for sound change are discussed.

Characterizing spoken responses in masked-onset priming of reading aloud using articulography.

A key method for studying articulatory planning at different levels of phonological organization is masked-onset priming. In previous work using that paradigm the dependent variable has been acoustic response time (RT). We used electromagnetic articulography to measure articulatory RTs and the articulatory properties of speech gestures in non-word production in a masked-onset priming experiment. Initiation of articulation preceded acoustic response onset by 199 ms, but the acoustic lag varied by up to 63 ms, depending on the phonological structure of the target. Onset priming affected articulatory response latency, but had no effect on gestural duration, inter-gestural coordination, or articulatory velocity. This is consistent with an account of the masked-onset priming effect in which the computation from orthography of an abstract phonological representation of the target is initiated earlier in the primed than in the unprimed condition. We discuss the implications of these findings for models of speech production and the scope of articulatory planning and execution.

Effects of Glottalisation, Preceding Vowel Duration, and Coda Closure Duration on the Perception of Coda Stop Voicing.

English has multiple potential acoustic cues to coda stop voicing, including the duration of the preceding vowel, the coda closure duration, and, in some varieties, glottalisation. Glottalisation associated with coda stops appears to be a recent change to Australian English (AusE) with younger speakers using glottalisation more than older speakers in production. Here we report on a study designed to examine AusE-speaking listeners' perception of cues to coda stop voicing. Listeners were presented with audio stimuli in which preceding vowel duration, coda closure duration, and the relative proportions of the rhyme that these occupy were manipulated and co-varied with the presence or absence of glottalisation. The results show that listeners used preceding vowel duration to cue coda stop voicing, and that coda closure duration was a weaker cue to voicing when not varied in conjunction with preceding vowel duration. In addition, glottalisation facilitated increased perception of coda voicelessness, even when paired with very long preceding vowels, which otherwise signal coda voicing. Although age-related differences in production have previously been reported, we found that both older and younger listeners used glottalisation similarly in perception. These results may provide support for a sound change led by a shift in perception.

Glottalisation, coda voicing, and phrase position in Australian English.

Glottalisation is an important cue to coda stop voicelessness, particularly for younger Australian English speakers who utilise glottalisation more than older speakers, suggesting a recent sound change. However, most previous studies of glottalisation in this variety of English have focussed on single word utterances, raising questions about whether glottalisation in those studies may have been prosodically conditioned rather than specific to the coda stop: Could the observed effect have been due to phrase-final creaky voice, which is acoustically similar to coda-related glottalisation? This study therefore explored the differential effects of phrase position on the production of glottalisation. Phrase-medially (where phrase-final creaky voice is not expected to occur), results confirmed previous findings that glottalisation cues coda stop voicelessness and that it does so more frequently for younger compared to older speakers. In phrase-final position, rates of glottalisation increased, but older speakers appeared more similar to younger speakers in use of glottalisation, suggesting that the change towards the increased use of glottalisation may be nearing completion in this prosodic position. Younger speakers appear to represent a more advanced stage of the change extending the use of glottalisation from phrase-final to phrase-medial position.

Effect of early dialectal exposure on adult perception of phonemic vowel length.

Attunement to native phonological categories and the specification of relevant phonological features in the lexicon occur early in development for monolingual and monodialectal speakers. However, few studies have investigated whether and how early exposure to two dialects of a language might influence the development of phonological categories, especially when a phonemic contrast exists only in one dialect. This study compared perceptual sensitivity to mispronunciations in phonemic vowel length in Australian English adult listeners with and without early exposure to another English dialect that did not have this contrast. The results showed that, while both mono- and bi-dialectal groups were sensitive to mispronunciations in vowel length, the bi-dialectal adults were more likely to accept a mispronunciation in vowel length compared to mono-dialectal adults. The bi-dialectal group accepted mispronunciations in vowel length more than in vowel height and backness. These results suggest that the bi-dialectal Australian English adults may employ a more flexible vowel length category for spoken word processing compared to mono-dialectal adults. The findings reveal a complex influence of early exposure to another dialect on the development of phonological categories.

Planning of Hiatus-Breaking Inserted /ɹ/ in the Speech of Australian English-Speaking Children.

Purpose: Non-rhotic varieties of English often use /ɹ/ insertion as a connected speech process to separate heterosyllabic V1.V2 hiatus contexts. However, there has been little research on children's development of this strategy. This study investigated whether children use /ɹ/ insertion and, if so, whether hiatus-breaking /ɹ/ can be considered planned, as evidenced by F3 lowering on V1. Method: Thirteen Australian English-speaking children (7 girls, 6 boys; mean age 6;1 [years;months]) participated in an elicited production task. The stimuli included carrier sentences containing 4 test words (linking /ɹ/ context: door, floor; intrusive /ɹ/ context: paw, claw) followed by of (e.g., "This is the paw of the cat"). After familiarization containing auditory and picture prompts, children produced test sentences upon presentation of picture prompts alone. Results: Eight children produced /ɹ/ insertion; the others used (some) glottalization. The incidence of /ɹ/ did not vary across linking or intrusive contexts, and inserted /ɹ/ was associated with F3 lowering at V1 onset relative to control items without /ɹ/. Conclusion: Six-year-old Australian English-speaking children who use /ɹ/ insertion show evidence of planning ahead and inserting /ɹ/ as a segment. The implications for the development of speech-planning processes and phonological and lexical representations are discussed.

The prosodic licensing of coda consonants in early speech: interactions with vowel length.

English has a word-minimality requirement that all open-class lexical items must contain at least two moras of structure, forming a bimoraic foot (Hayes, 1995).Thus, a word with either a long vowel, or a short vowel and a coda consonant, satisfies this requirement. This raises the question of when and how young children might learn this language-specific constraint, and if they would use coda consonants earlier and more reliably after short vowels compared to long vowels. To evaluate this possibility we conducted an elicited imitation experiment with 15 two-year-old Australian English-speaking children, using both perceptual and acoustic analysis. As predicted, the children produced codas more often when preceded by short vowels. The findings suggest that English-speaking two-year-olds are sensitive to language-specific lexical constraints, and are more likely to use coda consonants when prosodically required.

The syllabic status of final consonants in early speech: a case study.

Young children's first attempts at CVC words are often realized with the final consonant being heavily aspirated or followed by an epenthetic vowel (e.g. cat /kæt/ realized as [kæth] or [kætə]). This has led some to propose that young children represent word-final (coda) consonants as an onset-nucleus sequence (CV.Cv) (e.g. Goad & Brannen, 2003), raising questions about the syllabic status of the final consonant. To address this issue, we conducted an acoustic analysis of a child's early production of CVC, CVCh, and CVCV words between the ages of 1;3 and 1;5. Aside from aspiration, the results showed that there were no significant acoustic differences between the CVC and CVCh forms. In contrast, there were systematic acoustic differences in C2 closure duration between the CVC/CVCh and CVCV target words, suggesting that at least some children learning English have early coda representations for monosyllabic CVC words, whether heavily aspirated or not.

Three-year-olds' production of Australian English phonemic vowel length as a function of prosodic context.

Durational contrasts are used not only to signal phrasal boundaries and focused constituents, but also to make phonemic distinctions. Boundary and focus effects can therefore interact with phonemic length contrasts, presenting a challenge for learners. Boundary effects are most clearly seen in the syllable rhyme, where the nucleus and coda are longer in utterance-final compared to utterance-medial position, the magnitude of lengthening diminishing leftward from the end of the word. In the case of focus, where the nucleus and coda are also lengthened, the magnitude of lengthening diminishes rightwards toward the end of the word. The goal of this paper was therefore to compare productions of the phonemic vowel length contrast /ɐː/ vs /ɐ/ in adults and 3-yr-old children learning Australian English in the face of competing demands from boundary and focus lengthening. The results showed that the children maintain the /ɐː/ vs /ɐ/ contrast across prosodic contexts. They are also able to implement an adult-like pattern of boundary-related lengthening, but are still developing focus-related lengthening. The findings suggest that these 3-yr-olds have good command of the phonemic vowel length contrast, but are still fine-tuning language-specific aspects of temporal organization (i.e., the vowel-coda trading relationship) within the rhyme.

Acoustic investigations into the later acquisition of syllabic -es plurals.

PURPOSE: Children acquire /-z/ syllabic plurals (e.g., bus es) later than /-s, -z/ segmental plurals (e.g., cat s, dog s). In this study, the authors explored whether increased syllable number or segmental factors best explains poorer performance with syllabic plurals. METHOD: An elicited imitation experiment was conducted with 14 two-year-olds involving 8 familiar disyllabic target plural nouns, half with syllabic plurals (e.g., bus → bus es) and half with segmental plurals (e.g., letter → letter s). Children saw pictures of the target items on a computer and repeated prerecorded 3-word-utterances with the target word in utterance-medial position (e.g., "The buses come") and utterance-final position (e.g., "Hear the buses"). Acoustic analysis determined the presence or absence of the plural morpheme and its duration. RESULTS: Children had more trouble producing syllabic plurals compared with segmental plurals. Errors were especially evident in the utterance-medial position, where there was less time for the child to perceive/produce the word in the absence of phrase-final lengthening and where planning for the following word was still required. CONCLUSIONS: The results suggested that articulatory difficulties-rather than a word length effect-explain later acquisition of syllabic plurals relative to segmental plurals. These findings have implications for the nature of syllabic plural acquisition in children with hearing impairments and specific language impairment.

Side-hole fiber sensor based on surface plasmon resonance.

Surface plasmon resonance (SPR) is demonstrated in a microstructured optical fiber sensor for the first time (to our knowledge). SPR features were observed at 560 and 620 nm when sample fluids of refractive indices n=1.38 and n=1.41, respectively, were applied to the sensor. This study also identifies a new approach to improve the resolution of fiber SPR sensors.

Magnetic-resonance evaluation of the suitability of microstructured polymer optical fibers as sensors for ionic aqueous solutions.

Nuclear magnetic resonance was used to probe the distribution of water and ionic species in a microstructured poly(methyl methacrylate) (PMMA) polymer optical fiber (MPOF), with a plan to assess the suitability of these fibers for aqueous chemosensing. The NMR spectra and the measurements of proton spin relaxation in hydrated fibers demonstrated the presence of two distinct pools of water: water residing in the microstructure channels and the hydration water residing in the polymer matrix of the fiber. No facile chemical exchange between these two pools was present. The NMR peaks of the two pools of water were separated by 1.53 ppm. Relaxation measurements of the fiber samples doped with aqueous copper sulfate showed that charged ions freely entered the microstructure channels but were completely excluded from the polymer matrix of the fiber. Measurements of the apparent diffusion coefficient of water along the axial direction of the fiber showed that water molecules moved unimpeded along the channels. This is the first reported magnetic-resonance study of microstructured optical fibers. The findings suggest that microstructured PMMA fibers are compatible with ionic aqueous solutions and could provide a robust and durable platform for chemical-sensing applications.

Vowel transcription systems: An Australian perspective.

Transcription is an essential clinical tool for speech-language pathologists as it provides a permanent written record of communicative behaviour and forms an important source of data for analysis, interpretation, decision making, and dissemination. One of the responsibilities in speech-language pathology is to faithfully capture the speech production characteristics of clinical populations so that informed management decisions may be made. Notation systems that are appropriately suited for this purpose are mandatory. In Australia today, the conventional phonemic transcription system was first described over 60 years ago. However, an alternative to this traditional system has more recently been proposed by Harrington, Cox and Evans (HCE). This paper details the HCE system and argues its advantage as a clinical tool for speech-language pathologists in Australia. This new system provides a more accurate phonetically oriented foundation against which atypical vowel production can be assessed. It is further argued that the HCE system can form the basis for narrower phonetic examination and has pedagogical value in the description of Standard Australian English.

Opening up optical fibres.

A unique optical fibre design is presented in this work: a laterally accessible microstructured optical fibre, in which one of the cladding holes is open to the surrounding environment and the waveguide core exposed over long lengths of fibre. Such a fibre offers the opportunity of real-time chemical sensing and biosensing not previously possible with conventional microstructured optical fibres, as well as the ability to functionalize the core of the fibre without interference from the cladding. The fabrication of such a fibre using PMMA is presented, as well as experimental results demonstrating the use of the fibre as a evanescent wave absorption spectroscopy pH sensor using the indicator Bromothymol Blue.

Surface enhanced Raman scattering in a hollow core microstructured optical fiber.

Improvement of surface enhanced resonant Raman scattering (SERRS) signals is demonstrated by confining the scattering event to the core of a hollow core microstructured optical fiber. The analyte solution fills the entire microstructure. The pump light is guided in the liquid core and the Raman scattered signal is efficiently collected by the fiber and transmitted to the detector. Rhodamine 6G (210nM) adsorbed on silver nanoparticles in aqueous solution is used as a demonstration system and it was found that it is possible to collect usable Raman signals from the solution filled optical fiber well beyond the detection limit of an equivalent free-space system.

Fabrication and study of microstructured optical fibers with elliptical holes.

We report the fabrication of what are believed to be the first microstructured optical fibers with uniformly oriented elliptical holes. A high degree of hole ellipticity is achieved with a simple technique that relies on hole deformation during fiber draw. Both form and stress-optic birefringence are characterized over a broad wavelength range. These measurements are in excellent agreement with numerical modeling and demonstrate a birefringence as high as 1.0 x 10(-4) at a wavelength of 850 nm.