Clear speech production of Korean stops: changing phonetic targets and enhancement strategies.

The proposal that phonological contrast is enhanced through greater approximation of phonetic targets was investigated by comparing clear speech to conversational and citation-form speech produced by Korean speakers. The stop system of Korean is undergoing a sound change in which younger speakers produce the aspirated-lenis stop contrast differently from previous generations. Older speakers differentiate this contrast primarily with the acoustic correlate of voice onset time (VOT) and secondarily with F0. Younger speakers are merging VOT values for this contrast. As a result, the primary acoustic correlate is now F0 for younger speakers. These production differences likely indicate that younger speakers have developed different phonetic targets for stop production. These different phonetic targets were predicted to result in different enhancement patterns in clear speech: Younger speakers were predicted to enhance F0 differences, whereas older speakers were predicted to enhance VOT differences in clear speech. Results indicated that the older group solely used VOT to enhance the contrast in clear speech, whereas the younger group primarily used F0 but also demonstrated small VOT enhancement. These results indicate that clear speech enhancement strategies reflect phonetic targets. Older and younger speakers have different F0 and VOT targets and these different targets conditioned different enhancement strategies.

Phonological systems in bilinguals: age of learning effects on the stop consonant systems of Korean-English bilinguals.

Interaction of Korean and English stop systems in Korean-English bilinguals as a function of age of acquisition (AOA) of English was investigated. It was hypothesized that early bilinguals (mean AOA=3.8 years) would more likely be native-like in production of English and Korean stops and maintain greater independence between Korean and English stop systems than late bilinguals (mean AOA=21.4 years). Production of Korean and English stops was analyzed in terms of three acoustic-phonetic properties: voice-onset time, amplitude difference between the first two harmonics, and fundamental frequency. Late bilinguals were different from English monolinguals for English voiceless and voiced stops in all three properties. As for Korean stops, late bilinguals were different from Korean monolinguals for fortis stops in voice-onset time. Early bilinguals were not different from the monolinguals of either language. Considering the independence of the two stop systems, late bilinguals seem to have merged English voiceless and Korean aspirated stops and produced English voiced stops with similarities to both Korean fortis and lenis stops, whereas early bilinguals produced five distinct stop types. Thus, the early bilinguals seem to have two independent stop systems, whereas the late bilinguals likely have a merged Korean-English system.

Native Thai speakers' acquisition of English word stress patterns.

The influence of syllabic structure, lexical class and stress patterns of known words on the acquisition of the English stress system was investigated in ten native Thai speakers. All participants were adult learners of English with an average length of residence in the US of 1.4 years. They were asked to produce and give perceptual judgments on 40 English non-words of varying syllabic structures in noun and verb sentence frames. Results of the production data suggested that syllables with a long vowel attracted stress more often than syllables containing a short vowel and nouns received initial stress more often than verbs. Additionally, regression analyses with the three factors as predictors suggested that Thai participants' pattern of stress assignment on non-words was significantly influenced by the stress patterns of phonologically similar real words. These results were compared and contrasted to those found in previous work with Spanish-English and Korean-English bilinguals.

The vowel systems of Quichua-Spanish bilinguals. Age of acquisition effects on the mutual influence of the first and second languages.

This study investigates vowel productions of 20 Quichua-Spanish bilinguals, differing in age of Spanish acquisition, and 5 monolingual Spanish speakers. While the vowel systems of simultaneous, early, and some mid bilinguals all showed significant plasticity, there were important differences in the kind, as well as the extent, of this adaptability. Simultaneous bilinguals differed from early bilinguals in that they were able to partition the vowel space in a more fine-grained way to accommodate the vowels of their two languages. Early and some mid bilinguals acquired Spanish vowels, whereas late bilinguals did not. It was also found that acquiring Spanish vowels could affect the production of native Quichua vowels. The Quichua vowels were produced higher by bilinguals who had acquired Spanish vowels than those who had not. It is proposed that this vowel reorganization serves to enhance the perceptual distinctiveness between the vowels of the combined first- and second-language system.

Factors affecting stress placement for English nonwords include syllabic structure, lexical class, and stress patterns of phonologically similar words.

Seventeen native English speakers participated in an investigation of language users' knowledge of English main stress patterns. First, they produced 40 two-syllable nonwords of varying syllabic structure as nouns and verbs. Second, they indicated their preference for first or second syllable stress of the same words in a perception task. Finally, they indicated words they considered to be phonologically similar to the nonwords. Analyses of variance on the production and perception data indicated that both syllabic structure and lexical class (noun or verb) had an effect on main stress assignment. In logistic regression analyses on the production and perception responses. predictions of stress placement made by (1) syllable structure, (2) lexical class, and (3) stress patterns of phonologically similar words all contributed significantly and uniquely to the prediction of main stress assignment. The results indicate that phonological theories of English word stress need to allow for multiple, competing, probabilistic factors in accounts of main stress placement including syllabic structure (most notably vowel length), lexical class, and stress patterns of phonologically similar words.