Vowel Inherent Spectral Change Research Articles

Acoustic, phonetic, and phonological features of Drehu vowels.

This study presents an acoustic investigation of the vowel inventory of Drehu (Southern Oceanic Linkage), spoken in New Caledonia. Reportedly, Drehu has a 14 vowel system distinguishing seven vowel qualities and an additional length distinction. Previous phonological descriptions were based on impressionistic accounts showing divergent proposals for two out of seven reported vowel qualities. This study presents the first phonetic investigation of Drehu vowels based on acoustic data from eight speakers. To examine the phonetic correlates of the proposed phonological vowel inventory, multi-point acoustic analyses were used, and vowel inherent spectral change (VISC) was investigated (F1, F2, and F3). Additionally, vowel duration was measured. Contrary to reports from other studies on VISC in monophthongs, we find that monophthongs in Drehu are mostly steady state. We propose a revised vowel inventory and focus on the acoustic description of open-mid /ɛ/ and the central vowel /ə/, whose status was previously unclear. Additionally, we find that vowel quality stands orthogonal to vowel quantity by demonstrating that the phonological vowel length distinction is primarily based on a duration cue rather than formant structure. Finally, we report the acoustic properties of the seven vowel qualities that were identified.

Modeling vowel-inherent spectral change in varying consonant context

A wide variety of experimental evidence has shown that vowel inherent spectral change (VISC) is important in vowel identification. This evidence is drawn from production data, statistical pattern recognition, and perceptual experiments with both synthetic or manipulated naturally produced speech. Experimental studies often consider vowels in a constant consonant context which makes it difficult to factor out context effects from the VISC itself. In order to examine the magnitude of these consonant effects, we developed a statistical procedure inspired by Broad and Clermont [(2014). J. Phon. 47, 47–80] in which vowel formant frequencies are approximated by a linear combination of vowel and consonant influences which vary as a function of time. Vowels extracted from a database of both spontaneous and read speech were analyzed to produce context-normalized vowel-formant tracks. Results show that vowel formant frequencies vary systematically across their duration in both spontaneous and read speech and that all consonants in both onset and coda position show significant effects on vowel production across their entire duration. Although these formant patterns are seemingly complex, perceptual evidence suggests that listeners may only attend to onsets and offsets and that deviations from a straight-line interpolation between onset and offset must be relatively large for listeners to discriminate them.

Dynamic specification of vowels in Hijazi Arabic.

Research on various languages shows that dynamic approaches to vowel acoustics- in particular Vowel-Inherent Spectral Change (VISC)- can play a vital role in characterising and classifying monophthongal vowels compared with a static model. This study's aim was to investigate whether dynamic cues also allow for better description and classification of the Hijazi Arabic (HA) vowel system, a phonological system based on both temporal and spectral distinctions. Along with static and dynamic F1 and F2 patterns, we evaluated the extent to which vowel duration, F0, and F3 contribute to increased/decreased discriminability among vowels. Data were collected from 20 native HA speakers (10 females and 10 males) producing eight HA monophthongal vowels in a word list with varied consonantal contexts. Results showed that dynamic cues provide further insights regarding HA vowels that are not normally gleaned from static measures alone. Using discriminant analysis, the dynamic cues (particularly the seven-point model) had relatively higher classification rates, and vowel duration was found to play a significant role as an additional cue. Our results are in line with dynamic approaches and highlight the importance of looking beyond static cues and beyond the first twoformants for further insights into the description and classification of vowel systems.

Formant detail needed for identifying, rating, and discriminating vowels in Wisconsin English.

Neel [(2004). Acoust. Res. Lett. Online 5, 125-131] asked how much time-varying formant detail is needed for vowel identification. In that study, multiple stimuli were synthesized for each vowel: 1-point (monophthongal with midpoint frequencies), 2-point (linear from onset to offset), 3-point, 5-point, and 11-point. Results suggested that a 3-point model was optimal. This conflicted with the dual-target hypothesis of vowel inherent spectral change research, which has found that two targets are sufficient to model vowel identification. The present study replicates and expands upon the work of Neel. Ten English monophthongs were chosen for synthesis. One-, two-, three-, and five-point vowels were created as described above, and another 1-point stimulus was created with onset frequencies rather than midpoint frequencies. Three experiments were administered (n = 18 for each): vowel identification, goodness rating, and discrimination. The results ultimately align with the dual-target hypothesis, consistent with most vowel inherent spectral change studies.

The phonology of vowel VISC-osity – acoustic evidence and representational implications

While vowel inherent spectral change (VISC) is becoming increasingly prominent in phonetic descriptions of varieties of English, there is little data on whether and how formant dynamics may shape the vowel systems of other languages. This paper provides cross-language acoustic comparisons of the degree of VISC in Polish and British English. In one study, British English showed a greater concentration of F1 movement earlier in the time course of vowels than Polish. In a second study, proficient Polish speakers of English showed a greater concentration of F1 movement earlier in the time course of vowels while speaking their L2 English than while speaking their L1 Polish. These findings are in line with a proposal formulated in the Onset Prominence (OP) framework, by which the relative degree of formant dynamics in the two languages is attributable to consonantal or vocalic affiliation of the Vocalic Onset (VO) node of structure. Consonantal VO affiliation in English contributes to a greater degree of VISC concentrated earlier in vowel duration. Further empirical patterns associated with the OP representational settings in the two languages are also discussed, along with implications for other languages.

Self-perception and vowel inherent spectral change

Speakers self-correct vowels with deviant formants: tokens whose onsets are farther from the average midpoint move toward that average, while nearer tokens move randomly (Niziolek et al., 2013). The method used to establish this finding typically groups tokens based on onset formants relative to midpoint formants, and the midpoint is taken as the target. But vowel inherent spectral change research has shown that vowels are best modelled as contours rather than midpoints. The present study asks whether speakers self-correct toward trajectories rather than static midpoints. Seventeen female speakers provided 20 tokens of each stressed non-rhotic monophthong in English in [hVd] (heed, hid, etc.). Formants were sampled at 3% and 50% of vowel duration, and each speaker’s average formant position was calculated at both samples. Sample-matched Euclidean distances were calculated—each 3% token to the 3% average, each 50% token to the 50% average—rather than comparing to the midpoint sample in both cases. Tokens were grouped based on onset distance. Far tokens showed a larger decrease in distance by the midpoint than Near tokens, and regression to the mean was ruled out as the reason. This study suggests that speakers use dynamic spectral information for online self-correction.

Re-testing theories of vowel inherent spectral change

Three basic models of vowel inherent spectral change have been proposed: onset + offset, onset + direction, and onset + slope (or spectral rate of change). Morrison (2013) presents three theoretical stimuli whose identification rates relative to each other should lend weight to one of these hypotheses: (i) canonical duration and canonical onset-to-offset trajectory, (ii) canonical duration with double trajectory length, and (iii) canonical trajectory with half duration. The bulk of previous work supports onset + offset. In the present study, eight English monophthongs were synthesized with the Klatt synthesizer of the Berkeley Phonetics Machine. Three versions of each vowel were synthesized, corresponding to the theoretical stimuli of Morrison (2013). These 24 stimuli were used in two studies (n= 18 for each). First was a vowel identification task, where the choices were [hVd] words with the chosen vowels ( heed, hid, etc.). Second was a goodness rating task with a 7-point Likert scale, where participants were played a vowel stimulus while being shown the orthographic [hVd] word containing that vowel. The results do not fully support any one theory, but they align most closely with the onset + direction hypothesis, with onset + offset also being supported.

Patterns of Misidentified Vowels in Individuals With Dysarthria Secondary to Amyotrophic Lateral Sclerosis

Purpose The current study examines the pattern of misidentified vowels produced by individuals with dysarthria secondary to amyotrophic lateral sclerosis (ALS). Method Twenty-three individuals with ALS and 22 typical individuals produced 10 monophthongs in an /h/-vowel-/d/ context. One hundred thirty-five listeners completed a forced-choice vowel identification test. Misidentified vowels were examined in terms of the target vowel categories (front-back; low-mid-high) and the direction of misidentification (the directional pattern when the target vowel was misidentified, e.g., misidentification "to a lower vowel"). In addition, acoustic predictors of vowel misidentifications were tested based on log first formant (F1), log second formant, log F1 vowel inherent spectral change, log second formant vowel inherent spectral change, and vowel duration. Results First, high and mid vowels were more frequently misidentified than low vowels for all speaker groups. Second, front and back vowels were misidentified at a similar rate for both the Mild and Severe groups, whereas back vowels were more frequently misidentified than front vowels in typical individuals. Regarding the direction of vowel misidentification, vowel errors were mostly made within the same backness (front-back) category for all groups. In addition, more errors were found toward a lower vowel category than toward a higher vowel category in the Severe group, but not in the Mild group. Overall, log F1 difference was identified as a consistent acoustic predictor of the main vowel misidentification pattern. Conclusion Frequent misidentifications in the vowel height dimension and the acoustic predictor, F1, suggest that limited tongue height control is the major articulatory dysfunction in individuals with ALS. Clinical implications regarding this finding are discussed.

What Acoustic Studies Tell Us About Vowels in Developing and Disordered Speech.

Purpose Literature was reviewed on the development of vowels in children's speech and on vowel disorders in children and adults, with an emphasis on studies using acoustic methods. Method Searches were conducted with PubMed/MEDLINE, Google Scholar, CINAHL, HighWire Press, and legacy sources in retrieved articles. The primary search items included, but were not limited to, vowels, vowel development, vowel disorders, vowel formants, vowel therapy, vowel inherent spectral change, speech rhythm, and prosody. Results/Discussion The main conclusions reached in this review are that vowels are (a) important to speech intelligibility; (b) intrinsically dynamic; (c) refined in both perceptual and productive aspects beyond the age typically given for their phonetic mastery; (d) produced to compensate for articulatory and auditory perturbations; (e) influenced by language and dialect even in early childhood; (f) affected by a variety of speech, language, and hearing disorders in children and adults; (g) inadequately assessed by standardized articulation tests; and (h) characterized by at least three factors-articulatory configuration, extrinsic and intrinsic regulation of duration, and role in speech rhythm and prosody. Also discussed are stages in typical vowel ontogeny, acoustic characterization of rhotic vowels, a sensory-motor perspective on vowel production, and implications for clinical assessment of vowels.

Static and dynamic cues in vowel production in Hijazi Arabic

Static cues such as formant measurements obtained at the vowel midpoint are usually taken as the main correlate for vowel identification. However, dynamic cues such as vowel-inherent spectral change have been shown to yield better classification of vowels using discriminant analysis. The aim of this study is to evaluate the role of static versus dynamic cues in Hijazi Arabic (HA) vowel classification, in addition to vowel duration and F3, which are not usually looked at. Data from 12 male HA speakers producing eight HA vowels in /hVd/ syllables were obtained, and classification accuracy was evaluated using discriminant analysis. Dynamic cues, particularly the three-point model, had higher classification rates (average 95.5%) than the remaining models (static model: 93.5%; other dynamic models: between 65.75% and 94.25%). Vowel duration had a significant role in classification accuracy (average +8%). These results are in line with dynamic approaches to vowel classification and highlight the relative importance of cues such as vowel duration across languages, particularly where it is prominent in the phonology.

Modeling dynamic trajectories of front vowels in the American South

Regional variation in American English speech is often described in terms of shifts, indicating which vowel sounds are converging or diverging. In the U.S. South, the Southern vowel shift (SVS) and African American vowel shift (AAVS) affect not only vowels' relative positions but also their formant dynamics. Static characterizations of shifting, with a single pair of first and second formant values taken near vowels' midpoint, fail to capture this vowel-inherent spectral change, which can indicate dialect-specific diphthongization or monophthongization. Vowel-inherent spectral change is directly modeled to investigate how trajectories of front vowels /i eɪ ɪ ɛ/ differ across social groups in the 64-speaker Digital Archive of Southern Speech. Generalized additive mixed models are used to test the effects of two social factors, sex and ethnicity, on trajectory shape. All vowels studied show significant differences between men, women, African American and European American speakers. Results show strong overlap between the trajectories of /eɪ, ɛ/ particularly among European American women, consistent with the SVS, and greater vowel-inherent raising of /ɪ/ among African American speakers, indicating how that lax vowel is affected by the AAVS. Model predictions of duration additionally indicate that across groups, trajectories become more peripheral as vowel duration increases.

Variability of formant values at different time points of vowels

Vowel inherent spectral change research has led to two apparently contradictory conclusions about the appropriate representation of vowels: perception studies support a dual-target model of vowels, while production studies focus on calculating higher-fidelity continuous formant contours. This study explores production data in a new way by analyzing where in vowel duration variability is lowest across tokens. Portions of vowels that are less variable across tokens are assumed reflect greater importance to or planning by speakers. Born-and-raised Wisconsinites aged 18–30 were recorded reading a word-in-frame reading list eliciting 30 tokens of 14 American English vowels in the context /hVd/. F1 and F2 were sampled at 50 evenly spaced intervals for each vowel, covering the entire duration. For every speaker, the standard deviations of F1 and F2 were taken separately at every sample. Variability was analyzed as a function of time point. An upturned parabola pattern suggests a single target, a downturned parabola pattern suggests a dual target, and a horizontal pattern suggests continuous specification. For monophthongs, variability is found to be convex, and it is concave for diphthongs. This analysis does not support a dual-target model for monophthongs.

Vowel-Specific Intelligibility and Acoustic Patterns in Individuals With Dysarthria Secondary to Amyotrophic Lateral Sclerosis.

Purpose The purpose of the study was to investigate vowel-specific intelligibility and acoustic patterns of individuals with different severities of dysarthria secondary to amyotrophic lateral sclerosis (ALS). Method Twenty-three individuals with dysarthria secondary to ALS and 22 typically aging individuals participated as speakers. Participants with ALS were divided into 2 severity groups (severe, mild). For vowel-specific intelligibility data, 135 listeners participated in the study. Vowel-specific intelligibility, intrinsic vowel duration, 1st and 2nd formants (F1 and F2), vowel inherent spectral change (VISC), and absolute VISC were examined. Results A significant interaction between severity group and the vowel-specific intelligibility pattern as well as F1, F2 VISC, and absolute F2 VISC was observed. Specifically, individuals with severe dysarthria showed a significantly less intelligible /ɪ/ than /ɛ/, unlike individuals with mild dysarthria and typically aging individuals. In addition, vowel intelligibility of /ɪ/ showed the strongest association to the severity measures in individuals with ALS. A number of vowel-specific findings are reported in the acoustic variables. Acoustic correlates of vowel-specific intelligibility were identified. Conclusion Vowel-specific intelligibility patterns are different across severity groups; particularly, low intelligibility of /ɪ/ was noted in individuals with severe dysarthria. Individuals with dysarthria maintained the acoustic contrast in duration and F1 VISC among vowels but did not maintain the other spectral contrasts. Reduction of acoustic vowel space was observed primarily due to high F1 in high vowels in individuals with severe dysarthria. Regression findings suggest that the high F1 values of high and mid vowels and F2 reduction of high- and mid-front vowels decreased vowel-specific intelligibility. In addition, vowel duration influenced the vowel intelligibility of vowels that required short intrinsic vowel duration. Lastly, F2 VISC influenced the vowel intelligibility of /ɪ/. Overall, the vowel-specific intelligibility pattern is related to both vowel-specific characteristics and group-specific articulatory control dysfunction.

Spectral change and duration as cues in Australian English listeners' front vowel categorization.

Australian English /iː/, /ɪ/, and /ɪə/ exhibit almost identical average first (F1) and second (F2) formant frequencies and differ in duration and vowel inherent spectral change (VISC). The cues of duration, F1 × F2 trajectory direction (TD) and trajectory length (TL) were assessed in listeners' categorization of /iː/ and /ɪə/ compared to /ɪ/. Duration was important for distinguishing both /iː/ and /ɪə/ from /ɪ/. TD and TL were important for categorizing /iː/ versus /ɪ/, whereas only TL was important for /ɪə/ versus /ɪ/. Finally, listeners' use of duration and VISC was not mutually affected for either vowel compared to /ɪ/.

Polish listeners’ perception of vowel inherent spectral change in L2 English

Abstract This paper describes a perception experiment with Polish listeners involving vowel inherent spectral change (VISC) in L2 English. A forced-choice rhyming task employing the Silent Center (SC) paradigm revealed relatively uniform effects of stimulus type (SC, Initial, Middle, Final) on accuracy across two proficiency groups, despite greater overall accuracy on the part of the more proficient users. Analysis of individual vowel pairs used in the rhyming trials revealed some effects of proficiency on the degree to which formant movement in the stimuli affected identification accuracy. This research contributes to the relatively sparse literature on VISC in L2 acquisition. Phonological considerations underlying the degree of VISC in Polish and English are also discussed.

African American women's speech: Vowel inherent spectral change

African American women's speech: Vowel inherent spectral change

"Mummy, keep it steady": phonetic variation shapes word learning at 15 and 17 months.

Fifteen-month-olds have difficulty detecting differences between novel words differing in a single vowel. Previous work showed that Australian English (AusE) infants habituated to the word-object pair DEET detected an auditory switch to DIT and DOOT in Canadian English (CanE) but not in their native AusE (Escudero etal., ). The authors speculated that this may be because the vowel inherent spectral change variation (VISC) in AusE DEET is larger than in CanE DEET. We investigated whether VISC leads to difficulty in encoding phonetic detail during early word learning, and whether this difficulty dissipates with age. In Experiment 1, we familiarized AusE-learning 15-month-olds to AusE DIT, which contains smaller VISC than AusE DEET. Unlike infants familiarized with AusE DEET (Escudero etal., ), infants detected a switch to DEET and DOOT. In Experiment 2, we familiarized AusE-learning 17-month-olds to AusE DEET. This time, infants detected a switch to DOOT, and marginally detected a switch to DIT. Our acoustic analysis showed that AusE DEET and DOOT are differentiated by the second vowel formant, while DEET and DIT can only be distinguished by their changing dynamic properties throughout the vowel trajectory. Thus, by 17 months, AusE infants can encode highly dynamic acoustic properties, enabling them to learn the novel vowel minimal pairs that are difficult at 15 months. These findings suggest that the development of word learning is shaped by the phonetic properties of the specific word minimal pair.

Examining the effect of first formant transition on perception of dynamic spectral change in the second formant

Speech perception studies using methods such as formant-flattening and the silent-center paradigm have demonstrated that vowel-inherent spectral change (VISC) in speech-like stimuli adds significant information aiding in accurate phoneme identification. For listeners to reliably utilize this cue, formant extent thresholds must be smaller than transitions occurring in natural syllables. Although natural speech always involves movement of multiple formants over time, limited studies have determined formant transition thresholds in the context of competing formant movement. The purpose of this study was to begin to examine these interactions by determining the effect of F1-region transitions on perception of change in F2 (ΔF2). Listeners were presented 120 ms, two-formant stimuli approximating a vocoid F1/F2 configuration using a 4-interval, 2AFC, two-down/one-up adaptive paradigm. The first formant pivoted around a 500 Hz center frequency, and the second around 1500Hz. Thresholds for detection of both upwar...

Modeling consonant-context effects in a large database of spontaneous speech recordings.

Given recent interest in the analysis of naturally produced spontaneous speech, a large database of speech samples from the Canadian Maritimes was collected, processed, and analyzed with the primary aim of examining vowel-inherent spectral change in formant trajectories. Although it takes few resources to collect a large sample of audio recordings, the analysis of spontaneous speech introduces a number of difficulties compared to that of laboratory citation speech: Surrounding consonants may have a large influence on vowel formant frequencies and the distribution of consonant contexts is highly unbalanced. To overcome these problems, a statistical procedure inspired by that of Broad and Clermont [(2014). J. Phon. 47, 47-80] was developed to estimate the magnitude of both onset and coda effects on vowel formant frequencies. Estimates of vowel target formant frequencies and the parameters associated with consonant-context effects were allowed to vary freely across the duration of the vocalic portion of a syllable which facilitated the examination of vowel-inherent spectral change. Thirty-five hours of recorded speech samples from 223 speakers were automatically segmented and formant-frequency values were measured for all stressed vowels in the database. Consonant effects were accounted for to produce context-normalized vowel formant frequencies that varied across time.

Dynamic acoustic properties of monophthongs and diphthongs in Western Sydney Australian English.

This study provides a thorough acoustic analysis of the 18 Australian English monophthongs and diphthongs produced in a variety of phonetic contexts by young adult speakers from Western Sydney. The 18 vowels are well separated by duration and dynamic formant trajectory information. Vowel durations and formant trajectories were affected by the consonantal context in which the vowels were produced, particularly those produced in the /hVd/ context. Finally, the results indicate that capturing aspects of vowel inherent spectral change may be useful in future cross-dialectal and cross-linguistic studies.