増田 斐那子

A previous study found that spatial release from masking (SRM) could be observed under virtual reverberant environments using a first order Ambisonic-based sound reproduction system, however, poor localisation accuracy made it difficult to examine effect of varying reverberation time on SRM. The present study follows on using higher order Ambisonics (HOA) to examine how benefits from SRM vary in different spatial acoustics. Subjective speech intelligibility was measured where four room acoustics:reverberation time (RT)= 0.7 s (clarity (C50)= 15.9 dB, 6.8 dB) RT= 1.7 s (C50= 10.3 dB, 3.3 dB) were simulated via a third order Ambisonics system with a 16 channel spherical loudspeaker array. The masker was played from 8 azimuthal angles (0, ±45, ±90, ±135, 180 degrees) while the target speech was played from 0 degree. The listeners are deemed to benefit from SRM if their intelligibility scores were higher when the masker was projected from a different angle than that of the target. We found while listeners could benefit from SRM at C50 = 15.9 dB and 10.3 dB, the benefit starts to diminish at C50 = 6.8 dB, and listeners could no longer benefit from SRM at C50 = 3.3 dB.

Perceiving non-native sounds in adverse listening environments is challenging, even for proficient learners. An identification experiment in quiet, three reverberant (RT = 0.78 s, 1.12 s, 1.43 s) and multispeaker babble+reverberant environments was carried out to investigate the relation of listening environments and non-native language proficiency. This research aims to elucidate (1) Japanese and English listeners' identification of intervocalic English consonants in quiet and adverse listening environments, and (2) the correlation of identification rates with the Japanese listeners' TOEIC (R) scores, age of onset of English acquisition and length of residence in English-speaking countries. Results showed (1) English listeners achieved significantly higher overall identification rates compared to Japanese listeners on the subset of 11 consonants /f d(3) 3 l r s integral theta partial derivative v z/ that are often difficult for Japanese to accurately identify, and (2) positive correlations between identification rates and English proficiency measured by means of TOEIC (R) scores and LOR. Analysis of misperception patterns revealed that an increased amount of background disturbance led proficient listeners' misperception patterns to resemble those of the lower proficiency listeners, as in the example of native listeners misperceiving /g/ as /partial derivative/ in RT=1.12s and highly proficient Japanese misperceiving /g/ as /partial derivative/, /r/, and /l/, and lower group as /partial derivative/ and /l/. The degradation of identification accuracy as background disturbance increased shed light on how one's L1 and L2 proficiency influence speech perception. (c) 2016 Elsevier B.V. All rights reserved.

本研究では,日本語の下顎の開き具合がどのような音声要因によって決定されるかを検証した。EMAを用いた調音実験を用い,日本語話者の様々なCVモーラの発音時の顎の動きを測定した。結果として,母音では/a/>/e/>/o/>/i/>/u/という順番で顎の開きが大きいことが判明した。この結果から母音の高さ,前後性ともに顎の動きに影響するという結論を得た。顎の動きの大きさを,過去の日本語の音響研究と照合すると,F1と多少の相関があるが,母音長と最も強く相関することがわかった。また子音による顎の動きの阻害(inhibition)も観察された。子音による阻害は舌先音(coronal)でもっとも強く見られ,これは他の同時調音(coarticulation)に関する実験とも整合性がある。

A study was conducted to establish correlation between English proficiency and consonant identification ability during identification of English consonants in intervocalic contexts in multi-speaker babble noise by Japanese listeners. TOEIC scores and the number of months spent living in English-speaking countries were used to measure the Japanese participants' English proficiency. TOEIC was used to measure the Japanese participants? English proficiency, as it was widely used in Japanese universities as a means to evaluate students' English proficiency. The number of months spent in English-speaking countries was also used to investigate the correlation between English consonant identification under the assumption that listeners with a longer experience of residing in English-speaking countries were more used to and in need of perceiving English speech under a more or less adverse listening condition.

Listening to speech in noisy environments is more difficult than in quiet environments, especially for non-native listeners, even if their performance in quiet environments does not fall far below that of native listeners. The results showed that the bilinguals performance in adverse listening environments fell short of that of the native listeners with significant differences, even though the bilinguals attained perfect scores in a quiet environment. The bilingual participants were first exposed to Spanish from birth, and then to English before the age of six. This implies that even early bilinguals do not perform as well as native listeners in adverse environments and are likely to be influenced the language they were first exposed to. The use of background noise with various SNRs will also enable us to understand the mechanism of speech perception by learners with different proficiencies.

Numerous research has investigated how first language influences the perception of foreign sounds. The present study focuses on the perception of voiceless English fricatives by Japanese listeners with advanced and intermediate level English proficiency, and compares their results with that of English native listeners. Listeners identified consonants embedded in /a _ a/ in quiet, multi-speaker babble and white noise (SNR=0 dB). Results revealed that intermediate level learners scored the lowest among all listener groups, and /th/-s/ confusions were unique to Japanese listeners. Confusions of /th/-/f/ were observed among all listener groups, which suggest that those phoneme confusions may be universal.

Previous research has revealed that Japanese native speakers are highly likely to both perceive and produce epenthetic vowels between consonants. The goal of the present study is to investigate the influence of English learning backgrounds in the perception and production of consonant clusters by Japanese native speakers. In Experiment 1, a forced-choice AXB task to identify VC(u)CV is assigned to 17 highly fluent Japanese-English bilinguals and 22 Japanese monolinguals. Results show that monolinguals made significantly more errors than bilinguals. In Experiment 2, the influence of English proficiency on the production of consonant clusters, and the effect of consonant voicing on vowel epenthesis are investigated. The epenthetic vowels are acoustically analyzed and categorized into three degrees: full, partial and no epenthesis. The voicing combinations of the consonant clusters are C[+voice]-C[+voice], C[-voice]-C[+voice], and C[-voice]-C[-voice]. Results show that monolinguals inserted more epenthetic vowels than bilinguals, and that the influence of consonant voicing was stronger in monolinguals than bilinguals. Furthermore, monolinguals' epenthetic vowels between C[-voice]-C[+voice] and C[-voice]-C[-voice] tended to become devoiced than bilinguals. This result suggests a stronger L1 influence on monolinguals. The results of the two experiments thus suggest that the English proficiency influences the perception and production of consonant clusters. © 2010 The Acoustical Society of Japan.

Previous research has revealed that Japanese native speakers are more likely to perceive an 'illusory vowel' within consonant clusters compared to French native speakers (Dupoux et al. 1998). The aim of this research is to investigate the differences of perception and production of consonant clusters in Japanese-English bilinguals and Japanese monolinguals. The stimuli of the two experiments consist of 36 pseudo-words that contain the two sequences, VCCV and VCVCV. Results of the perception and the production experiments on the two groups of participants revealed that bilinguals were more likely to achieve high scores in both experiments.