Acoustic and perceptual similarity of Japanese and American English vowels

Australian English listeners' perception of Japanese vowel length reveals underlying phonological knowledge

Speech perception patterns are strongly influenced by one's native phonology. It is generally accepted that native English listeners rely primarily on spectral cues when perceiving vowels, making limited use of duration cues because English lacks phonemic vowel length. However, the literature on vowel perception by English listeners shows a marked bias toward American English, with the phonological diversity among different varieties of English largely overlooked. The current study investigates the perception of Japanese vowel length contrasts by native listeners of Australian English, which is reported to use length to distinguish vowels unlike most other varieties of English. Twenty monolingual Australian English listeners participated in a forced-choice experiment, where they categorized Japanese long and short vowels as most similar to their native vowel categories. The results showed a general tendency for Japanese long and short vowels (e.g., /ii, i/) to be categorized as Australian English long and short vowels (e.g., /i:, ɪ/ as in "heed," "hid"), respectively, which contrasts with American English listeners' categorization of all Japanese vowels as tense regardless of length (e.g., /ii, i/ as both "heed") as reported previously. Moreover, this duration-based categorization was found not only for Australian English categories that contrast in duration alone (e.g., /ɐ:, ɐ/ as in "hard," "hud") but also for those that contrast in both duration and spectra (e.g., /o:, ɔ/ as in "hoard," "hod"), despite their spectral mismatch from the corresponding Japanese vowels (e.g., /aa, a/ and /oo, o/). The results, therefore, suggest that duration cues play a prominent role across all vowel categories-even nonnative-for Australian English listeners. The finding supports a feature-based framework of speech perception, where phonological features like length are shared across multiple categories, rather than the segment-based framework that is currently dominant, which regards acoustic cues like duration as being tied to a specific native segmental category. Implications for second and foreign language learning are discussed.

Domain Generalization for Language-Independent Automatic Speech Recognition

A language-independent automatic speech recognizer (ASR) is one that can be used for phonetic transcription in languages other than the languages in which it was trained. Language-independent ASR is difficult to train, because different languages implement phones differently: even when phonemes in two different languages are written using the same symbols in the international phonetic alphabet, they are differentiated by different distributions of language-dependent redundant articulatory features. This article demonstrates that the goal of language-independence may be approximated in different ways, depending on the size of the training set, the presence vs. absence of familial relationships between the training and test languages, and the method used to implement phone recognition or classification. When the training set contains many languages, and when every language in the test set is related (shares the same language family with) a language in the training set, then language-independent ASR may be trained using an empirical risk minimization strategy (e.g., using connectionist temporal classification without extra regularizers). When the training set is limited to a small number of languages from one language family, however, and the test languages are not from the same language family, then the best performance is achieved by using domain-invariant representation learning strategies. Two different representation learning strategies are tested in this article: invariant risk minimization, and regret minimization. We find that invariant risk minimization is better at the task of phone token classification (given known segment boundary times), while regret minimization is better at the task of phone token recognition.

Cross-Linguistic Perceptual Categorization of the Three Corner Vowels: Effects of Listener Language and Talker Age

The present study examined the center and size of naïve adult listeners' vowel perceptual space (VPS) in relation to listener language (LL) and talker age (TA). Adult listeners of three different first languages, American English, Greek, and Korean, categorized and rated the goodness of different vowels produced by 2-year-olds and 5-year-olds and adult speakers of those languages, and speakers of Cantonese and Japanese. The center (i.e., mean first and second formant frequencies (F1 and F2)) and size (i.e., area in the F1/F2 space) of VPSs that were categorized either into /a/, /i/, or /u/ were calculated for each LL and TA group. All center and size calculations were weighted by the goodness rating of each stimulus. The F1 and F2 values of the vowel category (VC) centers differed significantly by LL and TA. These effects were qualitatively different for the three vowel categories: English listeners had different /a/ and /u/ centers than Greek and Korean listeners. The size of VPSs did not differ significantly by LL, but did differ by TA and VCs: Greek and Korean listeners had larger vowel spaces when perceiving vowels produced by 2-year-olds than by 5-year-olds or adults, and English listeners had larger vowel spaces for /a/ than /i/ or /u/. Findings indicate that vowel perceptual categories of listeners varied by the nature of their native vowel system, and were sensitive to TA.

Vowel Length Expands Perceptual and Emotional Evaluations in Written Japanese Sound-Symbolic Words

In this study, we examined whether vowel length affected the perceptual and emotional evaluations of Japanese sound-symbolic words. The perceptual and emotional features of Japanese sound-symbolic words, which included short and long vowels, were evaluated by 209 native Japanese speakers. The results showed that subjective evaluations of familiarity, visual imageability, auditory imageability, tactile imageability, emotional valence, arousal, and length were significantly higher for sound-symbolic words with long vowels compared to those with short vowels. Additionally, a subjective evaluation of speed was significantly higher for written Japanese sound-symbolic words with short vowels than for those with long vowels. The current findings suggest that vowel length in written Japanese sound-symbolic words increases the perceptually and emotionally subjective evaluations of Japanese sound-symbolic words.

Japanese Perceptual Epenthesis is Modulated by Transitional Probability

Perceptual epenthesis is the perception of illusory vowels in consonantal sequences that violate native phonotactics. The consensus has been that each language has a single, predictable candidate for perceptual epenthesis, that vowel which is most minimal (i.e., shortest and/or quietest). However, recent studies have shown that alternate epenthetic vowels can be perceived when the perceptual epenthesis of the minimal vowel would violate native co-occurrence restrictions. We propose a potential explanation for these observed patterns: speech perception, and thus also vowel perceptual epenthesis, is modulated by transitional probability whereby epenthetic vowels must conform to the language specific expectations of the listener. To test this explanation, we present two experiments examining perceptual epenthesis of two Japanese vowels-/u/ and /i/-against their transitional probability in CV sequences. In Experiment 1, Japanese listeners assigned VCCV tokens to VCuCV and VCiCV categories. In Experiment 2, participants discriminated VCCV tokens from VCuCV and VCiCV tokens. The results show that sequences where /i/ is transitionally probable are more likely to elicit /i/ perceptual epenthesis.

Native non-prototypicality in vowel perception induces prominent neuromagnetic mismatch intensities in non-native speakers: a pilot study

Neural mismatch response resulting from the difference between prediction and observation is related to change detection and discrimination. Robust neuromagnetic brain activity of auditory mismatch-related perception occurs in response to non-prototypical vowels in across-category contrasts for first-language speakers. However, whether this non-prototypicality effect applies to within-category vowel perception remains to be elucidated. Here, healthy Japanese adults (n = 7) were subjected to magnetoencephalography (MEG) while watching a silent movie, and passively listened to synthesized English vowels /i/. We observed the source-level mismatch effect to the mid-high near-front vowel deviant [ɪ] with the most non-prototypical, unspecified feature in the participants' native language system. The mismatch effect recruited the left posterior superior temporal sulcus with a peak latency of 225 ms post-stimulus onset. We further studied whether a longer F1 distance between vowel pairs would increase mismatch-activated intensities, however, we did not observe neuromagnetic changes when the prototypical anchor standard [i] was compared with three non-prototypical deviants differing in first resonance frequency (F1) values. Our results indicate that an F1 increase in within-category upper front vowel perception is a strong activator of mismatch responses measured by source-level activated intensities for non-native listeners.

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.

Vowel Duration Discrimination of Children With Childhood Apraxia of Speech: A Preliminary Study

Purpose The ability of 5- and 6-year-old male children (23 participants) between the chronological ages of 5;0 and 6;11 (years;months) with childhood apraxia of speech (CAS; n = 9) and with typical development (TD; n = 14) to detect differences in vowel duration of syllable pairs is explored. We asked whether the children with CAS show different patterns of performance on the vowel duration difference experimental task than those of their similarly aged peers with TD. Method A male adult audio-recorded the syllable /bɑ/. The /ɑ/ was digitally lengthened and shortened, while maintaining uniform fundamental frequency and amplitude of the vowel and duration of the consonant /b/ at 42 ms. Vowel lengths increased in 40-ms increments, ranging from 208 to 488 ms. Eight pairs of syllables, 1 with equal length and 7 with differing vowel lengths, were randomly presented to the children 10 times in blocks of 16 pairs via a computer application. Results Numerous complementary analyses indicated patterns of performance differed for children with CAS compared to the children with TD. The children with CAS were notably less accurate in their duration discrimination and evidenced greater variability in their performances across duration difference conditions than their peers with TD, signifying they were generally challenged to discriminate the vowel duration differences. Conclusion These results suggest that CAS, which is more generally considered a motor speech disorder, may have a perceptual component of CAS related to vowel duration discrimination. Further research directions and clinical implications are discussed. Supplemental Material https://doi.org/10.23641/asha.8411876.

Acoustic Sources of Accent in Second Language Japanese Speech

This study reports an exploratory analysis of the acoustic characteristics of second language (L2) speech which give rise to the perception of a foreign accent. Japanese speech samples were collected from American English and Mandarin Chinese speakers ( n = 16 in each group) studying Japanese. The L2 participants and native speakers ( n = 10) provided speech samples modeling after six short sentences. Segmental (vowels and stops) and prosodic features (rhythm, tone, and fluency) were examined. Native Japanese listeners ( n = 10) rated the samples with regard to degrees of foreign accent. The analyses predicting accent ratings based on the acoustic measurements indicated that one of the prosodic features in particular, tone (defined as high and low patterns of pitch accent and intonation in this study), plays an important role in robustly predicting accent rating in L2 Japanese across the two first language (L1) backgrounds. These results were consistent with the prediction based on phonological and phonetic comparisons between Japanese and English, as well as Japanese and Mandarin Chinese. The results also revealed L1-specific predictors of perceived accent in Japanese. The findings of this study contribute to the growing literature that examines sources of perceived foreign accent.

Re-Examining Phonetic Variability in Native and Non-Native Speech

BACKGROUND/AIMS

Non-native speech is frequently characterized as being more variable than native speech. However, the few studies that have directly investigated phonetic variability in the speech of second language learners have considered a limited subset of native/non-native language pairings and few linguistic features.

METHODS

The present study examines group-level withinspeaker variability and central tendencies in acoustic properties of vowels andstops produced by learners of Japanese from two native language backgrounds, English and Mandarin, as well as native Japanese speakers.

RESULTS

Results show that non-native speakers do not always exhibit more phonetic variability than native speakers, but rather that patterns of variability are specific to individual linguistic features and their instantiations in L1 and L2.

CONCLUSION

Adopting this more nuanced approach to variability offers important enhancements to several areas of linguistic theory.

Stress-Induced Acoustic Variation in L2 and L1 Spanish Vowels

AIM

We assessed the effect of lexical stress on the duration and quality of Spanish word-final vowels /a, e, o/ produced by American English late intermediate learners of L2 Spanish, as compared to those of native L1 Argentine Spanish speakers.

METHODS

Participants read 54 real words ending in /a, e, o/, with either final or penultimate lexical stress, embedded in a text and a word list. We measured vowel duration and both F1 and F2 frequencies at 3 temporal points.

RESULTS

stressed vowels were longer than unstressed vowels, in Spanish L1 and L2. L1 and L2 Spanish stressed /a/ and /e/ had higher F1 values than their unstressed counterparts. Only the L2 speakers showed evidence of rising offglides for /e/ and /o/. The L2 and L1 Spanish vowel space was compressed in the absence of stress.

CONCLUSION

Lexical stress affected the vowel quality of L1 and L2 Spanish vowels. We provide an up-to-date account of the formant trajectories of Argentine River Plate Spanish word-final /a, e, o/ and offer experimental support to the claim that stress affects the quality of Spanish vowels in word-final contexts.

Perception of American English vowels by sequential Spanish-English bilinguals

Research on American-English (AE) vowel perception by Spanish-English bilinguals has focused on the vowels /i/-/ɪ/ (e.g., in sheep/ship). Other AE vowel contrasts may present perceptual challenges for this population, especially those requiring both spectral and durational discrimination. We used Event-Related Potentials (ERPs), MMN (Mismatch Negativity) and P300, to index discrimination of AE vowels /ɑ/-/ʌ/ by sequential adult Spanish-English bilingual listeners compared to AE monolinguals. Listening tasks were non-attended and attended, and vowels were presented with natural and neutralized durations. Regardless of vowel duration, bilingual listeners showed no MMN to unattended sounds, and P300 responses were elicited to /ɑ/ but not /ʌ/ in the attended condition. Monolingual listeners showed pre-attentive discrimination (MMN) for /ɑ/ only; while both vowels elicited P300 responses when attended. Findings suggest that Spanish-English bilinguals recruit attentional and cognitive resources enabling native-like use of both spectral and durational cues to discriminate between AE vowels /ɑ/ and /ʌ/.

Successful non-native speech perception is linked to frequency following response phase consistency

Some people who attempt to learn a second language in adulthood meet with greater success than others. The causes driving these individual differences in second language learning skill continue to be debated. In particular, it remains controversial whether robust auditory perception can provide an advantage for non-native speech perception. Here, we tested English speech perception in native Japanese speakers through the use of frequency following responses, the evoked gamma band response, and behavioral measurements. Participants whose neural responses featured less timing jitter from trial to trial performed better on perception of English consonants than participants with more variable neural timing. Moreover, this neural metric predicted consonant perception to a greater extent than did age of arrival and length of residence in the UK, and neural jitter predicted independent variance in consonant perception after these demographic variables were accounted for. Thus, difficulties with auditory perception may be one source of problems learning second languages in adulthood.

Directional Asymmetries in Vowel Perception of Adult Nonnative Listeners Do Not Change Over Time With Language Experience

PURPOSE

This study tested an assumption of the Natural Referent Vowel (Polka & Bohn, 2011) framework, namely, that directional asymmetries in adult vowel perception can be influenced by language experience.

METHOD

Data from participants reported in Escudero and Williams (2014) were analyzed. Spanish participants categorized the Dutch vowels /aː/ and /ɑ/ in 2 separate sessions: before and after vowel distributional training. Sessions were 12 months apart. Categorization was assessed using the XAB task, where on each trial participants heard 3 sounds sequentially (first X, then A, then B) and had to decide whether X was more similar to A or B.

RESULTS

Before training, participants exhibited a directional asymmetry in line with the prediction of Natural Referent Vowel. Specifically, Spanish listeners performed worse when the vowel change from X to A was a change from peripheral to central vowel (/ɑ/ to /aː/). However, this asymmetry was maintained 12 months later, even though distributional training improved vowel categorization performance.

CONCLUSIONS

Improvements in adult nonnative vowel categorization accuracy are not explained by attenuation of directional asymmetries. Directional asymmetries in vowel perception are altered during native language acquisition, but may possibly be impervious to nonnative language experiences in adulthood.

Goodness and Accentedness Ratings of /hVt/ Tokens by Aware and Naive Listeners

PURPOSE

This study compares goodness and accentedness ratings of speech tokens rated by listeners who are naive to and aware of speakers' native language backgrounds. Listener responses to open-ended questions regarding goodness and accentedness ratings are also examined.

METHOD

Twenty-eight monolingual speakers of U.S. English served as listeners. Listeners were presented with 5 blocks of /hVt/ tokens. Each block represented a different vowel target and comprised correct and incorrect productions from English, Spanish, Korean, and Japanese speakers. Listeners rated goodness and accentedness using a 9-point Likert scale and explained their decision-making criteria when judging goodness versus accentedness.

RESULTS

There is a high positive correlation between goodness and accentedness. Both naive and aware listeners assigned poorer ratings when judging goodness compared with accentedness, but results varied on the basis of target accuracy. Aware listeners assigned better goodness and accentedness ratings compared with naive listeners. This difference was highly statistically significant. Both accentedness and goodness ratings are susceptible to listener bias.

CONCLUSIONS

Goodness and accentedness are highly correlated yet distinct measures. Goodness is more reflective of target accuracy than is accentedness. Native English tokens were affected by listener bias to a greater extent than nonnative English tokens.

Aging Effect on Korean Female Voice: Acoustic and Perceptual Examinations of Breathiness

OBJECTIVE

This paper sought to examine perceptual and acoustic characteristics in Korean female voices, focusing on the 'breathy' quality as a function of aging. In addition, we aimed to investigate if the three selected measures, H1-H2, H1-A1, and H1-A3, demonstrated any changes along a sustained vowel production.

PARTICIPANTS AND METHODS

A total of 42 participants were assigned to two age groups, young women and elderly women. All participants were asked to sustain /a/ as long and as steadily as possible. Perceptual judgments of breathiness were made on the GRBAS scale and by a direct magnitude estimation technique, while three acoustic parameters, H1-H2, H1-A1, and H1-A3, were measured at five measurement time points during the sustained vowel test.

RESULTS

Results indicated that the H1-H2 and H1-A1 values were significantly lower for elderly women compared to young women, although no difference in the perceptual estimation of breathiness was found between the age groups. Among the acoustic measures, only H1-A1 was significantly regressed against the perceptual estimate of breathiness. In addition, no significant acoustic difference in the measures was found across the five measurement points.

CONCLUSION

Our findings suggest that the aging voice might not be universally characterized by the breathy quality, which hints at the need for further research on ethnic diversity in vocal quality.

Using multiple measures to document change in English vowels produced by Japanese, Korean, and Spanish speakers: the case for goodness and intelligibility

PURPOSE

This study examined the effectiveness of using goodness ratings and intelligibility scores to document changes in vowel production following pronunciation training. The relationship between listener perceptions of goodness and intelligibility was also examined.

METHOD

Fifteen English language learner speakers (5 Japanese, 5 Korean, and 5 Spanish) participated in 16 sessions of vowel-focused pronunciation training. Pre- and posttraining judgments of 10 English vowels in /hVt/ context were conducted by 25 monolingual English speakers who served as listeners. Listeners judged vowel intelligibility using a 10-alternative forced-choice task and rated goodness using a 5-point Likert scale.

RESULTS

Goodness ratings and intelligibility scores captured improvement in the accuracy of several vowels following training. However, some vowels that received better mean intelligibility scores received poorer mean goodness ratings following training. The relationship between goodness ratings and intelligibility scores revealed that vowels such as /æ/ and /ʌ/ were more dependent on goodness for intelligibility than vowels such as /i/ and /e/, which were highly intelligible even when they received poor goodness ratings.

CONCLUSION

English vowels differ with respect to the importance of goodness for accurate identification by listeners. As such, clinicians should examine both goodness and intelligibility when measuring change following pronunciation training.

Influences of listeners' native and other dialects on cross-language vowel perception

This paper examines to what extent acoustic similarity between native and non-native vowels predicts non-native vowel perception and whether this process is influenced by listeners' native and other non-native dialects. Listeners with Northern and Southern British English dialects completed a perceptual assimilation task in which they categorized tokens of 15 Dutch vowels in terms of English vowel categories. While the cross-language acoustic similarity of Dutch vowels to English vowels largely predicted Southern listeners' perceptual assimilation patterns, this was not the case for Northern listeners, whose assimilation patterns resembled those of Southern listeners for all but three Dutch vowels. The cross-language acoustic similarity of Dutch vowels to Northern English vowels was re-examined by incorporating Southern English tokens, which resulted in considerable improvements in the predicting power of cross-language acoustic similarity. This suggests that Northern listeners' assimilation of Dutch vowels to English vowels was influenced by knowledge of both native Northern and non-native Southern English vowel categories. The implications of these findings for theories of non-native speech perception are discussed.

Cross-language perception of Japanese vowel length contrasts: comparison of listeners from different first language backgrounds

PURPOSE

The purpose of this research was to compare the perception of Japanese vowel length contrasts by 4 groups of listeners who differed in their familiarity with length contrasts in their first language (L1; i.e., American English, Italian, Japanese, and Thai). Of the 3 nonnative groups, native Thai listeners were expected to outperform American English and Italian listeners, because vowel length is contrastive in their L1. Native Italian listeners were expected to demonstrate a higher level of accuracy for length contrasts than American English listeners, because the former are familiar with consonant (but not vowel) length contrasts (i.e., singleton vs. geminate) in their L1.

METHOD

A 2-alternative forced-choice AXB discrimination test that included 125 trials was administered to all the participants, and the listeners' discrimination accuracy (d') was reported.

RESULTS

As expected, Japanese listeners were more accurate than all 3 nonnative groups in their discrimination of Japanese vowel length contrasts. The 3 nonnative groups did not differ from one another in their discrimination accuracy despite varying experience with length contrasts in their L1. Only Thai listeners were more accurate in their length discrimination when the target vowel was long than when it was short.

CONCLUSION

Being familiar with vowel length contrasts in L1 may affect the listeners' cross-language perception, but it does not guarantee that their L1 experience automatically results in efficient processing of length contrasts in unfamiliar languages. The extent of success may be related to how length contrasts are phonetically implemented in listeners' L1.

Perception of English vowels by bilingual Chinese-English and corresponding monolingual listeners

This study compares the underlying perceptual structure of vowel perception in monolingual Chinese, monolingual English and bilingual Chinese-English listeners. Of particular interest is how listeners' spatial organization of vowels is affected either by their L1 or their experience with L2. Thirteen English vowels, /i, I, e, epsilon, ae, u, omega, o, (see symbol), alpha, (see symbol)I, alphaI, alphaomega/, embedded in /hVd/ syllable produced by an Ohio male speaker were presented in pairs to three groups of listeners. Each listener rated 312 vowel pairs on a nine-point dissimilarity scale. The responses from each group were analyzed using a multidimensional scaling program (ALSCAL). Results demonstrated that all three groups of listeners used high/low and front/back distinctions as the two most important dimensions to perceive English vowels. However, the vowels were distributed in clusters in the perceptual space of Chinese monolinguals, while they were appropriately separated and located in that of bilinguals and English monolinguals. Besides the two common perceptual dimensions, each group of listeners utilized a different third dimension to perceive these English vowels. English monolinguals used high-front offset. Bilinguals used a dimension mainly correlated to the distinction of monophthong/diphthong. Chinese monolinguals separated two high vowels, /i/ and /u/, from the rest of vowels in the third dimension. The difference between English monolinguals and Chinese monolinguals evidenced the effect of listeners' native language on the vowel perception. The difference between Chinese monolinguals and bilingual listeners as well as the approximation of bilingual listeners' perceptual space to that of English monolinguals demonstrated the effect of L2 experience on listeners' perception of L2 vowels.

Auditory contrast versus compensation for coarticulation: data from Japanese and English listeners

English listeners categorize more of a [k-t] continuum as "t" after [character: see text] than [s] (Mann & Repp, 1981). This bias could be due to compensation for coarticulation (Mann & Repp, 1981) or auditory contrast between the fricatives and the stops (Lotto & Kluender, 1998). In Japanese, surface [[character: see text]k, [character: see text] t, sk, st] clusters arise via palatalization and vowel devoicing from /sik, sit, suk, sut/, and acoustic vestiges of the devoiced vowels remain in the fricative. On the one hand, compensation for coarticulation with the devoiced vowel would cancel out compensation for coarticulation with the fricative, and listeners would not show any response bias. On the other hand, if the stop contrasts spectrally with the fricative, listeners should respond "t" more often after [[character: see text] i] than [s[character: see text]]. Experiment I establishes that [k] and [t] coarticulate with preceding voiced [i, u], voiceless [[character: see text], [character: see text]], and [[character: see text], s]. Experiment 2 shows that both Japanese and English listeners respond "t" more often after [characters: see text] than [s[character: see text]], as predicted by auditory contrast. English listeners' "t" responses also varied after voiced vowels, but those of Japanese listeners did not. Experiment 3 shows that this difference reflects differences in their phonetic experience.

The Development of English Vowel Perception in Monolingual and Bilingual Infants: Neurophysiological Correlates

The goal of this paper was to examine intrinsic and extrinsic factors contributing to the development of speech perception in monolingual and bilingual infants and toddlers. A substantial number of behavioral studies have characterized when infants show changes in behavior towards speech sounds in relation to amount of experience with these sounds. However, these studies cannot explain to what extent the developmental timeline is influenced by experience with the language versus constraints imposed by cortical maturation. Studies using electrophysiological measures to examine the development of auditory and speech processing have shown great differences in infant and adult electrophysiological correlates of processing. Many of these differences are a function of immature cortex in the infant. In this paper, we examined the maturation of infant and child event-related-potential (ERP) electrophysiological components in processing an English vowel contrast and explored to what extent these components are influenced by intrinsic (e.g., sex) versus extrinsic factors, such as language experience (monolingual vs. bilingual). Our findings demonstrate differences in the pattern of ERP responses related to age and sex, as well as language experience. These differences make it clear that general maturational factors need to be taken into consideration in examining the effect of language experience on the neurodevelopment of speech perception.

Context-specific acoustic differences between Peruvian and Iberian Spanish vowels

This paper examines four acoustic properties (duration F0, F1, and F2) of the monophthongal vowels of Iberian Spanish (IS) from Madrid and Peruvian Spanish (PS) from Lima in various consonantal contexts (/s/, /f/, /t/, /p/, and /k/) and in various phrasal contexts (in isolated words and sentence-internally). Acoustic measurements on 39 speakers, balanced by dialect and gender, can be generalized to the following differences between the two dialects. The vowel /a/ has a lower first formant in PS than in IS by 6.3%. The vowels /e/ and /o/ have more peripheral second-formant (F2) values in PS than in IS by about 4%. The consonant /s/ causes more centralization of the F2 of neighboring vowels in IS than in PS. No dialectal differences are found for the effect of phrasal context. Next to the between-dialect differences in the vowels, the present study finds that /s/ has a higher spectral center of gravity in PS than in IS by about 10%, that PS speakers speak slower than IS speakers by about 9%, and that Spanish-speaking women speak slower than Spanish-speaking men by about 5% (irrespective of dialect).

A one-year longitudinal study of English and Japanese vowel production by Japanese adults and children in an English-speaking setting

The effect of age of acquisition on first- and second-language vowel production was investigated. Eight English vowels were produced by Native Japanese (NJ) adults and children as well as by age-matched Native English (NE) adults and children. Productions were recorded shortly after the NJ participants' arrival in the USA and then one year later. In agreement with previous investigations [Aoyama, et al., J. Phon. 32, 233-250 (2004)], children were able to learn more, leading to higher accuracy than adults in a year's time. Based on the spectral quality and duration comparisons, NJ adults had more accurate production at Time 1, but showed no improvement over time. The NJ children's productions, however, showed significant differences from the NE children's for English "new" vowels /ɪ/, /ε/, /ɑ/, /ʌ/ and /ʊ/ at Time 1, but produced all eight vowels in a native-like manner at Time 2. An examination of NJ speakers' productions of Japanese /i/, /a/, /u/ over time revealed significant changes for the NJ Child Group only. Japanese /i/ and /a/ showed changes in production that can be related to second language (L2) learning. The results suggest that L2 vowel production is affected importantly by age of acquisition and that there is a dynamic interaction, whereby the first and second language vowels affect each other.

A cross-dialect acoustic description of vowels: Brazilian and European Portuguese

This paper examines four acoustic correlates of vowel identity in Brazilian Portuguese (BP) and European Portuguese (EP): first formant (F1), second formant (F2), duration, and fundamental frequency (F0). Both varieties of Portuguese display some cross-linguistically common phenomena: vowel-intrinsic duration, vowel-intrinsic pitch, gender-dependent size of the vowel space, gender-dependent duration, and a skewed symmetry in F1 between front and back vowels. Also, the average difference between the vocal tract sizes associated with /i/ and /u/, as measured from formant analyses, is comparable to the average difference between male and female vocal tract sizes. A language-specific phenomenon is that in both varieties of Portuguese the vowel-intrinsic duration effect is larger than in many other languages. Differences between BP and EP are found in duration (BP has longer stressed vowels than EP), in F1 (the lower-mid front vowel approaches its higher-mid counterpart more closely in EP than in BP), and in the size of the intrinsic pitch effect (larger for BP than for EP).

Nonnative speech perception training using vowel subsets: effects of vowels in sets and order of training

PURPOSE

K. Nishi and D. Kewley-Port (2007) trained Japanese listeners to perceive 9 American English monophthongs and showed that a protocol using all 9 vowels (fullset) produced better results than the one using only the 3 more difficult vowels (subset). The present study extended the target population to Koreans and examined whether protocols combining the 2 vowel sets would provide more effective training.

METHOD

Three groups of 5 Korean listeners were trained on American English vowels for 9 days using one of the 3 protocols: fullset only, first 3 days on subset then 6 days on fullset, or first 6 days on fullset then 3 days on subset. Participants' performance was assessed by pre- and posttraining tests, as well as by a midtraining test.

RESULTS

(a) Fullset training was effective for Koreans as well as Japanese, (b) no advantage was found for the 2 combined protocols over the fullset-only protocol, and (c) sustained "nonimprovement" was observed for training using one of the combined protocols.

CONCLUSIONS

In using subsets for training on American English vowels, care should be taken not only in the selection of subset vowels but also in the training orders of subsets.