Vowel Quality Research Articles

The Effect of Pitch Accent on the Perception of English Lexical Stress: Evidence from English and Mandarin Chinese Listeners

The relative weighting of f0 and vowel reduction in English spoken word recognition at the sentence level were investigated in one two-alternative forced-choice word identification experiment. In the experiment, an H* pitch-accented or a deaccented word fragment (e.g., AR- in the word archive) was presented at the end of a carrier sentence for identification. The results of the experiment revealed differences in the cue weighting of English lexical stress perception between native and non-native listeners. For native English listeners, vowel quality was a more prominent cue than f0, while native Mandarin Chinese listeners employed both vowel quality and f0 in a comparable fashion. These results suggested that (a) vowel reduction is superior to f0 in signaling initial stress in the words and (b) f0 facilitates the recognition of word initial stress, which is modulated by first language.

Speech adaptation in conversation: Effects of segment cue-weighting strategy for non-native speakers

Research has investigated how speakers make phonetic adaptations by adjusting their speech sounds to either converge to or diverge from their interlocutor’s. Less is known about the dynamic adaptive strategies non-native speakers use to improve intelligibility when interacting with native speakers, particularly how their strategies change over the course of spontaneous conversations. The current study examines phonetic adaptations in English words contrasting tense and lax vowels (e.g., sheep-ship) in unscripted conversations between non-native Japanese English and native English speakers during an engaging computer game task. Japanese speakers have previously been found to rely on temporal cues (vowel length) for tensity distinctions due to their L1 cue-weighting strategy rather than spectral cues (vowel quality) that are predominantly used in English. Acoustic analyses are conducted to examine changes in non-native vowel productions before, during and after the conversation task. We predict that, in an attempt to overcome miscommunication, non-native speakers may initially lengthen the tense vowels to distinguish them from their lax counterparts. As the conversation progresses, non-native speakers may adapt to a more native-like cue-weighting pattern by shifting to spectral distinctions. Results are discussed in terms of adaptations to cue-weighting strategies for intelligibility gains by interlocutors of different linguistic backgrounds.

A vowel research retrospective

One of the earliest attempts at describing/characterizing vowel quality was Daniel Jones’ Cardinal Vowel system (1918) representing the total range of vowel quality in languages. It was based on auditory quality (evaluated by a trained phonetician). Much later, Ladefoged (1967) demonstrated that despite auditory equivalence, vowels were acoustically different—a function of physiological and production among speakers. The acoustic nature of vowel quality was elaborated through the introduction of easy spectral analysis (using the sonograph) exemplified by the seminal work by Peterson and Barney (1952). In the past five decades we have seen how vowels differ as a function of speaker sex, speaker size, age, speech disorder and dialect group and development of vowel spaces in second-language acquisition (much of the research through contributions of speakers in this session). In concert with these acoustic studies, we have better understanding of the nature of the perception of vowels through multidimensional scaling studies, adaptation/perceptual magnet/categorical perception studies, cross-linguistic studies, and developmental studies. Most recently, we have seen work done with regard to brain mapping and neural models of vowel perception. This talk will provide a review of past vowel research (voluminous as it is) and possible future trends.

Limits of short-term perceptual training for enhancing Seoul-Korean listeners’ use of English lexical stress in spoken word recognition

This study investigates whether short-term perceptual training can enhance Seoul-Korean listeners’ use of English lexical stress in spoken word recognition. Unlike English, Seoul Korean does not have lexical stress (or lexical pitch accents/tones). Seoul-Korean speakers at a high-intermediate English proficiency completed a visual-world eye-tracking experiment adapted from Connell et al. (2018) (pre-/post-test). The experiment tested whether pitch in the target stimulus (accented versus unaccented first syllable) and vowel quality in the lexical competitor (reduced versus full first vowel) modulated fixations to the target word (e.g., PARrot; ARson) over the competitor word (e.g., paRADE or PARish; arCHIVE or ARcade). In the training (eight 30-min sessions over eight days), participants heard English lexical-stress minimal pairs uttered by four talkers (high variability) or one talker (low variability), categorized them as noun (first-syllable stress) or verb (second-syllable stress), and received accuracy feedback. The results showed that neither training increased target-over-competitor fixation proportions. Crucially, the same training had been found to improve Seoul- Korean listeners’ recall of English words differing in lexical stress (Tremblay et al., 2022) and their weighting of acoustic cues to English lexical stress (Tremblay et al., 2023). These results suggest that short-term perceptual training has a limited effect on target-over-competitor word activation.

My great big problem with vowels

How vowels are produced in a second language (L2) is determined by several factors. One is cross-language mapping: how/if vowels in the L2 phonetic system are categorized in terms of native language (L1) vowels and the extent to which they are judged to resemble the L1 vowels perceptually. Another is input: the quantity and quality of the L2 vowels to which learners have been exposed. L1- L2 mapping patterns are sometimes reported in studies of L2 vowel learning, but they may differ across individuals and change as learners gain L2 experience. Coarse estimates of quantity of L2 input are usually reported but estimates of exposure to foreign-accented L2 input are virtually non-existent. Even if we had adequate measures of L2 input, other serious problems would remain. Once the L1 phonetic system is established, language users may attend less to the surface phonetic properties of vowels they hear when conversing in the L1 and also in the L2. This talk will focus on problems inherent in (a) understanding how the phonetic input received in an L2 is used, and (b) gauging degree of L2 learning success.

Vowel quantity/quality redux: Revisiting vowel contrasts in Hakha Lai monophthongs

Previous scholars have documented a phonemic length distinction in the monophthongal vowels of Hakha Lai, a Tibeto-Burman language spoken in Chin State in western Myanmar (Melnik, 1997; Peterson, 2003; Maddieson, 2004). In a previous pilot study of data from two college-aged speakers (the first instrumental acoustic analysis of Hakha Chin vowel quality), our findings revealed stark individual differences: one speaker showed robust quantity and minor quality differences, while for the other, neither duration nor quality played key roles; rather, her system had merged. Maddieson (2004) proposed that the length associated with long vowels in Hakha Lai is mainly realized through lengthening of sonorant codas; we did not find this to be the case for either speaker. However, those pilot data were limited both in terms of sample size and age range. Therefore, to expand on our previous findings, we now present analysis of data from fourteen talkers, including both a group of nine college aged talkers (6 women) and five older talkers (2 women, ages 46 and 77; 3 men, ages 48, 60, and 62). Duration and quality measures are reported for all monophthongs in all possible syllable shapes.

Vocalic contrasts in Zotung

Though very few Maraic languages from the South Central branch of Tibeto-Burman are represented in the existing body of phonetics literature, they are of interest in that they appear to contain typologically unique dense high vowel systems. Zotung, spoken by approximately 100 000 people in Chin State in western Burma and in diaspora communities, is one such language (Eberhard et al., 2022). The only linguistic scholarship on Zotung (Shintani, 2015) is an extensive wordlist with brief preliminary comments on the syllable shape, tone, and vowel inventories; however, acoustic analyses are absent. To augment Shintani (2015) and further elucidate the vowel inventory of Zotung, we present data from an older male speaker deeply involved with Zotung translation, preservation, and literacy efforts, who hails originally from Tingsi on the far southern border of the Zotung speaking area. Based on analysis of 553 tokens collected via a wordlist, we substantiate some of the findings reported by Shintani (2015) and document several important differences. Shintani reported 8 monophthongal vowel qualities; we find 10: [i, y, e, ø, æ, ə, a, u, o, ɔ]. Shintani also reported an expansive diphthong inventory; our data support this claim, with 9 total vowels that can be categorized as diphthongs.

Lexical Stress Identification in Cochlear Implant-Simulated Speech by Non-Native Listeners.

This study investigates whether a presumed difference in the perceptibility of cues to lexical stress in spectro-temporally degraded simulated cochlear implant (CI) speech affects how listeners weight these cues during a lexical stress identification task, specifically in their non-native language. Previous research suggests that in English, listeners predominantly rely on a reduction in vowel quality as a cue to lexical stress. In Dutch, changes in the fundamental frequency (F0) contour seem to have a greater functional weight than the vowel quality contrast. Generally, non-native listeners use the cue-weighting strategies from their native language in the non-native language. Moreover, few studies have suggested that these cues to lexical stress are differently perceptible in spectro-temporally degraded electric hearing, as CI users appear to make more effective use of changes in vowel quality than of changes in the F0 contour as cues to linguistic phenomena. In this study, native Dutch learners of English identified stressed syllables in CI-simulated and non-CI-simulated Dutch and English words that contained changes in the F0 contour and vowel quality as cues to lexical stress. The results indicate that neither the cue-weighting strategies in the native language nor in the non-native language are influenced by the perceptibility of cues in the spectro-temporally degraded speech signal. These results are in contrast to our expectations based on previous research and support the idea that cue weighting is a flexible and transferable process.

Interior Vowels in Complete [ATR] Systems of the Macro-Sudan Belt

The paper presents a typological overview of interior vowels in complete [ATR] systems of the Macro-Sudan Belt. Interior vowels are defined as vowel qualities within the interior regions of the vowel space and include front rounded vowels, all non-low central vowels and unrounded non-low back vowels. Complete [ATR] systems are defined as those systems where there is a cross-height contrast for the feature [ATR] (advanced tongue root) for non-low peripheral vowels and cross-height harmony both in static patterns (vowel co-occurence restrictions within morphemes) and dynamic patterns (restrictions within phonological domains comprising several morphemes). The study based on the sample of 35 languages of the Macro-Sudan Belt revealed three main types of interiority — allophonic, phonemic and epenthetic. These types are not sporadically distributed in terms of genetic affiliation and areal spreading of the languages. At least three clusters may be identified in the sample: (1) the Eastern Kru languages spoken in the Ivory Coast with numerous phonemic interior vowels specified for [ATR], (2) the Talodi languages of Sudan with one neutral interior vowel and (3) the North Guang languages with centralised allophones of front vowels appearing in inter-consonantal position. The territory of Ghana and Togo occupied by North Guang languages also includes a number of languages from the sample which belong to other families and exhibit different types of interiority. This region appears to be particularly rich both in languages showing the co-occurrence of complete [ATR] systems with interior vowels and in interiority types.

Development of language-specific stress discrimination in European Portuguese: an electrophysiological study.

European Portuguese (EP) is a language with unpredictable stress. Previous behavioral studies have shown that without vowel reduction EP adult speakers displayed a stress deafness effect akin to that observed in speakers of fixed-stress languages, suggesting that vowel quality may be the primary cue for stress discrimination in EP. However, an event-related potentials (ERPs) study reported that EP adults were able to discriminate stress contrasts pre-attentively in the absence of vowel quality cues. These results seemed to indicate that EP adult speakers may attend to different cues in the attentive and pre-attentive stress perception. Moreover, both the behavioral and ERPs studies have revealed a processing advantage for iambic stress, which could not be predicted by the rhythmic properties of EP, the language-specific weighting of stress correlates, or the frequency distributions of trochaic and iambic stresses in EP. A recent eye-tracking study has found that EP-learning infants at 5-6 months already exhibited an iambic preference in the absence of vowel reduction, manifested by longer looking time at the iambic stress. The present study used a passive oddball paradigm to examine pre-attentive stress perception without vowel quality cues by 5-to-7-month-old EP-learning infants. Results from twenty-two participants showed that both the trochaic and iambic conditions yielded a positive discrimination response (p-MMR). In addition, the iambic condition elicited a prominent late discriminative negativity (LDN) as well as a P3a component. Our findings present the first evidence for reciprocal discrimination of stress patterns in EP-learning infants, showing that, as in adult speakers, stress processing might also differ at the pre-attentive and attentive stages in infants. Importantly, the stress perception ability in EP-learning infants seems to develop asymmetrically, with an advantage for the iambic stress pattern. The present study highlighted the role of language-specific factors that may affect developing stress perception.

Production of English Vowel Contrasts in Spanish L1 Learners: A Longitudinal Study

The present study undertakes a longitudinal examination of forty postgraduate students, native Spanish speakers, during their first year at a UK university. The research focuses on both individual and collective progress in mastering distinctions within English vowel pairs (/iː/-/ɪ/, /ɪ/-/e/, and /uː/-/ʊ/), with a specific focus on adaptations towards achieving native-like English vowel pronunciation, particularly in terms of vowel quality. Prior research indicates that adult Spanish learners encounter difficulties in mastering the intricate linguistic nuances presented by English. The methodology involved recording Spanish-speaking participants reading a list of words (CVC context) at three different time points over a year. The analysis was based on formant frequencies using Praat, and Euclidean distances were calculated to represent the degree of separation between each pair of vowels. Information about external factors potentially influencing the development of vowel productions among speakers was gathered through a language background questionnaire. The outcomes suggested varying rates of advancement within the group, which could be attributed to the diverse levels of exposure and interaction with native English speakers during their year of study in the UK. These results affirm the learning processes in adult L2 production, emphasizing the critical role played by both the quantity and quality of time in the assimilation of pronunciations to novel L2 segments.

Sketches of chimpanzee (Pan troglodytes) hoo’s: vowels by any other name?

In human speech, the close back rounded vowel /u/ (the vowel in “boot”) is articulated with the tongue arched toward the dorsal boundary of the hard palate, with the pharyngeal cavity open. Acoustic and perceptual properties of chimpanzee (Pan troglodytes) hoo’s are similar to those of the human vowel /u/. However, the vocal tract morphology of chimpanzees likely limits their phonetic capabilities, so that it is unlikely, or even impossible, that their articulation is comparable to that of a human. To determine how qualities of the vowel /u/ may be achieved given the chimpanzee vocal tract, we calculated transfer functions of the vocal tract area for tube models of vocal tract configurations in which vocal tract length, length and area of a laryngeal air sac simulacrum, length of lip protrusion, and area of lip opening were systematically varied. The method described is principally acoustic; we make no claim as to the actual shape of the chimpanzee vocal tract during call production. Nonetheless, we demonstrate that it may be possible to achieve the acoustic and perceptual qualities of back vowels without a reconfigured human vocal tract. The results, while tentative, suggest that the production of hoo’s by chimpanzees, while achieving comparable vowel-like qualities to the human /u/, may involve articulatory gestures that are beyond the range of the human articulators. The purpose of this study was to (1) stimulate further simulation research on great ape articulation, and (2) show that apparently vowel-like phenomena in nature are not necessarily indicative of evolutionary continuity per se.

Developmental Changes in Acoustic Characteristics of Speech of Estonian Adolescents

The paper introduces the Estonian Adolescent Speech Corpus and explores the developmental changes in speech production based on acoustic characteristics of fundamental frequency (F0), formant frequencies, and speech tempo as a function of age and gender. Age- and gender-related anatomic changes in adolescence have implications for speech acoustics: a sudden drop of F0 at puberty in boys, and an almost gradual decrease of the acoustic vowels space. In parallel with anatomic changes, the development of the speech motor system is manifested as the increase of speaking rate. The analysis of fundamental frequency (F0) shows that in both male and female speakers, the F0 decreases gradually at the age from 9 to 12 years, then in males F0 drops ca by 100 Hz at the age of 12–15 due to puberty voice change, and becomes stable at the age of 15–18; in female speakers, a gradual decrease of F0 continues till the age 18. The formant frequencies of vowels decrease gradually from 10 to 15 years in both genders and the quality of vowels stabilizes at the age of 15–18 years, gender-specific differences emerge at the age of 12–13. Speech rate increases from 4 syllables per second in 9–10 years to 5.1 syllables per second in 14 years and becomes stable between the ages of 15 and 18, gender differences are not significant. The results of the current study can be considered as reference data that are typical for Estonian-speaking individuals aged 9–18 years with normal language development.

Acoustic adjustments of clear speech in Korean heritage vowel production

Aims and objectives: This study aims to explore the segmental and suprasegmental acoustic adjustments in the clear speech of Korean vowels produced by English-dominant Korean-heritage speakers and native Korean speakers. Methodology: Native Korean students at a university in the United States and Korean-American students enrolled in an intermediate Korean language course at the same university read isolated sentences featuring three representative Korean vowels (i.e., /i, a, u/), once in casual speech, and once in clear speech. They repeated this sequence five times. Data and analysis: The vowel space of the first and second formants (F1 and F2) in the clear speech was expanded for both heritage and native speakers, and the heritage vowel space was more fronted than the native vowel space, suggesting the influence of English among heritage speakers. However, the peripheral extent and direction in the clear speech and the dominant language effect in heritage speakers were inconsistent across the vowels. Also, pitch dynamics were highly significant in clear speech, exhibiting the salient fundamental frequency (F0) rising at the syllable offset for both heritage and native speakers. The vowel length enhancement in the clear speech was also confirmed in both native and heritage Korean vowels. Conclusions: The results confirmed the cross-language tendency in clear speech to induce the modification of vowel quality, pitch, and duration, which also applies to Korean heritage vowel production. Furthermore, the asymmetrical acoustic modifications across the vowels in heritage clear speech support the Speech Learning Model (SLM) prediction. Originality and implications: The findings present new data for the clear speech effects of Korean heritage vowel production and a further enhancement strategy of syllable offset pitch raising in clear speech for both native and heritage groups. The results contribute to the theoretical implication of bilingualism by connecting the SLM premise and heritage clear speech.

Phonetic correlates to Khalkha Mongolian vowel contrasts: duration, formants and voice quality

The paper reports the results of an analysis of acoustic correlates to phonological contrasts in vowel length, quality and pharyngeal width with data from five native speakers of the Khalkh dialect. The study replicates Svantesson’s (1985) discovery of a chain-shift rotation of the round vowels in their presumed evolution from Classical Mongolian. Analysis with VoiceSauce (Shue et al. in: Proceedings of the ICPhS XVII, 1846–1849, 2009) finds that in addition to the first formant, the harmonics-to-noise ratio is a reliable indicator of the ATR versus RTR contrast that has been hypothesized to be the basis of the language’s vowel harmony.

On the small flat vowel systems of Australian languages

The vowel systems of Australian languages could best be characterized as “small and flat.” Small, because about 50% of Australian languages have a three-vowel system with another 20% or so distinguishing four or five vowel qualities. Flat, because, while there is the usual degree of separation between front and back vowels along the horizontal (F2) axis of the vowel space (700–2400 Hz), variation along the vertical (F1) axis is typically restricted to a range of 350-900 Hz, leaving the ‘close’ vowel area noticeably under-exploited. Thus, rather than the [i, a, u] values as traditionally transcribed, 3-vowel languages have the phonetic (Cardinal Vowel) qualities of [e, ɐ, o] and 5-vowel languages have [e, ɛ, ɐ, ɔ, o]. I suggest that, as with the atypical consonant inventories, the lack of close vowels in these languages may be explained in terms of the historical influence of the hearing status of their speakers. Reduction in vowel space in individual speakers is one consequence of hearing impairment caused by otitis media, which can reduce hearing levels under 500 Hz by up to 40 dB. The Australian Aboriginal population has the highest prevalence of otitis media in the world by far (50 to 90%).

The effect of perceived human-likeness on voice-user interface–directed speech

Many interact daily with voice–user interfaces (VUIs), but acoustic research on VUI-directed speech (VDS) is relatively new. Prior work indicates intensity and F0 correlate with VDS [Cohn et al., 2022, JPhon 90]. Multiple acoustic variables of VDS were analyzed to explore if VDS is a register distinct from human-directed speech (HDS) and whether perceived human-likeness of VUI voices affects VDS characteristics. 27 participants’ Zoom recordings of 13 pre-scripted prompts and pre-recorded responses from two Amazon AWS-Polly-generated VUI voices (rated for human-likeness independently and by participants) were acoustically analyzed for word-initial voiceless plosives voice onset time (VOT), pitch variation, and vowel quality and quantity. Results of linear mixed-effects models indicate evidence of VDS-specific acoustic characteristics, some of which are affected by participants’ perceived human-likeness of the voices. Differences in pre-exposure and VUI interactions occur for /p/ VOT in consonant clusters, vowel duration (except /ɪ/), and /ɑ/ F2. Statistical differences are found for /p/ VOT in consonant clusters and vowel quality (e.g., /ɑ/ F1 and F2, and /ɪ/ F2) based on perceived human-likeness by participants. This study contributes to the growing VDS work examining how humans speak with devices and what affects VDS, which may influence considerations of VUI voice development.

An acoustic examination of Drehu vowels

Drehu is an indigenous language spoken in New Caledonia. Compared to other Oceanic languages, it has rather large vowel and consonantal inventories. The vowel system consists of 14 vowels, distinguishing seven vowel qualities and an additional length distinction. Previous phonological studies showed divergent proposals for two of the vowel qualities /ɛ/ and /ə/ based on impressionistic descriptions. For this study, data was collected through a controlled reading task that was conducted during a fieldwork trip. We investigate the Drehu vowels for the first time, using acoustic data from eight native speakers (4 female). Vowel duration, formant values and dynamic formant properties were measured to examine the phonetic correlates of the proposed phonological vowel quality and length distinctions. In this study, we report seven timbres identified across the fourteen vowels of the system. Our results confirm a distinction between phonologically long and short vowels based on duration differences. We provide a detailed acoustic description of the vowel system and propose a revised vowel inventory based on a detailed analysis of formant structure of open-mid /ɛ/ and the central vowel /ə/.

The vowel inventory of Nakanamanga

Nakanamanga is an Oceanic language spoken by approximately 10,000 speakers in central Vanuatu (Lynch and Crowley, 2001), including northern Efate island and Nguna and other small islands to the north. Previous work on Nakanamanga indicates that it has five distinctive vowel qualities (/i,e,a,o,u/), as is typical of Oceanic languages, and some evidence of long vowels (Schütz, 1969). However, whether vowel length is contrastive remains unclear, and there are suggestions that vowel length exhibits complex relationships with consonantal and prosodic patterns (Schütz, 1969; McClintock, 1991; Schmidt, 2023). We present findings of a pilot study targeting vowel length in Nakanamanga, based on phonological evidence and acoustic phonetic data. A wordlist consisting of words of CVCV structures was designed after consultation with a native speaker, and recorded with the speaker in Mere-Sauwia village on Nguna. Data was processed and analysed using Praat, EMU-SDMS and R (Boersma and Weenink, 2023; Winkelmann et al., 2017; R Core Team, 2023). Results for vowel duration and first and second formant frequency at vowel midpoints provide strong evidence that Nakanamanga has ten distinct vowels, with a length contrast for all five vowel qualities. Findings lay the groundwork for larger-scale investigations of the phonetics and phonology of Nakanamanga.

What does it mean to sound Korean-Canadian, eh? A comparative study on Canadian English vowel space

Existing research on Canadian English shows evidence of dialectal differences between regions. Not only are there differences based on region, but groups (e.g., heritage, immigrant) in these respective regions are not participating in the ongoing sound changes of Canadian English (e.g., Canadian Raising) to the same degree. In respect to sound changes, studies have found that some sounds are undergoing more drastic change than others, young female groups are usually more advanced in the progress, and that the largest heritage groups in major Canadian cities (Toronto, Vancouver, Montreal) are participating in sound changes—with some reported differences in vowel quality. This study extends the existing literature on Canadian sound changes by investigating the acoustic vowel quality of Korean heritage speakers in Vancouver. The speech of 11 monolingual Canadian English speakers and 22 Korean heritage speakers were analyzed for specific sound patterns (/u/-fronting, /æ/ raising) as well as overall vowel space area. This study finds that Korean heritage speakers also participate in the ongoing sound changes (e.g., /u/-fronting) but there are also some notable differences in their vowel acoustics, when compared to their monolingual counterparts.