北原 真冬

It is well attested that vowels are longer before voiced than voiceless consonants in English. Vowel duration in productions by American English speakers (AE) is affected especially by the voicing of postvocalic consonants and the quality of the target vowel [1]. Similar voicing effects in Japanese infants and adults, and also in English produced by Japanese learners (JE) were found as well [2]. However, previous studies on voicing effects in JE overlooked an important factor: gemination in loanwords. Data from a production experiment using monosyllabic English words with and without gemination in their borrowed counterparts were analyzed. Participants were 15 university students in Tokyo from intermediate to advanced proficiency levels in English, and two AE speakers for control. Results showed that vowel duration for JE was conditioned not by post-vocalic voicing, but instead by geminatability of the word, which was independently judged by 12 Japanese listeners in a different experiment. Post-vocalic stop closure duration was longer for voiceless than voiced stops, and longer for words that were judged to have a geminate stop than words that did not, for JE but not for AE speakers. Thus, voicing effects attested in AE speech is not straightforwardly realized in JE because of the interference from Japanese prosody.

Research on Tohoku dialects, which is a variety of Japanese, has found that the voiceless stops /k/ and /t/ in the intervocalic position are frequently realized as voiced stops. However, the phenomenon has mainly been judged aurally in the Japanese linguistics literature and has not been confirmed by acoustic measurements. We measured the VOT of data originally collected in the survey of Tohoku dialects by [1]. The data used in this study includes two age groups from eight sites. The results demonstrate that for word medial stops, the VOT distribution of voiced and voiceless stops largely overlapped, while, the laryngeal contrast was maintained for the word initial stops. Intervocalic voicing neutralization was confirmed by quantitative acoustic measurements. The effects of neighboring vowels were also investigated to show that height, but not duration, had a significant effect on voicing neutralization. Our results shed light on the phonetic nature of Tohoku dialects as well as on their phonological structure, such as the role of voicing contrast.

Alveolar flaps are non-contrastive allophonic variants of alveolar stops in American English. A lexical decision experiment was conducted with Japanese learners of English (JE) to investigate whether second-language (L2) learners are sensitive to such allophonic variations when recognizing words in L2. The stimuli consisted of 36 isolated bisyllabic English words containing word-medial /t/, half of which were flapfavored words, e.g. city, and the other half were [t]-favored words, e.g. faster. All stimuli were recorded with two surface forms: /t/as a flap, e.g. city with a flap, or as [t], e.g. city with [t]. The stimuli were counterbalanced so that participants only heard one of the two surface forms of each word. The accuracy data indicated that flap-favored words pronounced with a flap, e.g. city with a flap, were recognized significantly less accurately than flap-favored words with [t], e.g. city with [t], and [t]-favored words with [t], e.g. faster with [t]. These results suggest that JE learners prefer canonical forms over frequent forms produced with context-dependent allophonic variations. These results are inconsistent with previous studies that found native speakers' preference for frequent forms, and highlight differences in the effect of allophonic variations on the perception of native-language and L2 speech.

英語母音の持続時間が有声子音の前では無声子音の前よりも1.5倍ほど長いという現象は,一般に有声効果(voicing effect)と呼ばれ,英語特有の現象とされてきた。しかしながら,多くの実験結果から,有声効果は英語のみならず他言語にも見られることが明らかになってきた。例えば,有声効果は普遍的な音声メカニズムに起因するという考えがある一方で(Ko 2007),英語の1.5倍という効果の大きさには個別文法が関係しているという見方(House 1961)もある。本稿では,まず普遍的なメカニズムに起因するという仮説を検証するため,NTT乳幼児音声データベース(Amano,Kondo,Kato and Nakatani 2009)と日本語話し言葉コーパス(Maekawa 2003)を用いて幼児および成人の日本語話者における有声効果の有無を検証した。その上で,英語の大きな有声効果を日本人英語学習者が獲得可能であるかどうか,習熟度によって分けた2群の被験者の産出データから検討した。その結果,有声効果は普遍的・音声的な基盤を持ちながらも,言語個別の音韻特質によって抑制・促進されうる可能性が高いことを明らかにした。

The functional load of phonemes is a long-standing, but not a main-stream notion in modern linguistics: that some pairs of phonemes distinguish more words than other pairs is intuitively plausible, but hard to quantify. Meanwhile, neighborhood effects in word recognition and production have been one of the central topics in psycholinguistics, leading to a wide variety of investigations. However, the Greenberg-Jenkins calculation, the most common definition of phonological neighborhood, deals only with deletion, addition, and substitution of phonemes, lacking any consideration of prosody. For example, homophones, which cannot be segmental neighbors and thus excluded in most neighborhood research, can be distinctive if lexical accent is specified. The role of onset/rhyme distinction in neighborhood calculation has been discussed, but morae, another basic unit of prosody, were not mentioned in the literature. We propose a novel method for calculating the functional load based on a prosodically extended neighborhood analysis. It is a frequency-weighted neighborhood density summed across neighbors for a particular phoneme. Accentual distinctions, morae or syllables, and context effects within a word are taken into account. The proposed method gives a better account for the difference in the acquisition order of segments across languages. © 2013 Acoustical Society of America.

The current study examined the acoustic modifications of the lexical pitch accent in Tokyo Japanese infant-directed speech (IDS), with the focus on the F0 fall delay, where the alignment of the F0 turning points associated with pitch accents were delayed with respect to the accented mora. The AIKEN Mother-Infant Conversation Corpus (R-JMICC) [1] produced by 21 mothers from Tokyo area, was used to investigate the alignment of the F0 turning points. Two-piece linear regression was used to locate the turning points and the frequency of F0 fall delay was computed in IDS and in adult-directed speech (ADS). The results revealed that the frequency of F0 fall delay depended on the syllable structures of the accented syllable as well as the prosodic conditions (the presence of the boundary pitch movements and non-lexical lengthening) typically observed in Japanese IDS. We found significantly more frequent F0 fall delay in IDS compared to ADS, when the prosodic conditions were taken into account. The results indicate that the language-specific prosodic structure should be considered in order to characterize the F0 fall delay of lexical pitch accents in IDS.

理研母子会話コーパス,およびその収録に付随して行った読み上げ課題のデータを用いて,対乳児発話(IDS)と対成人発話(ADS)のピッチについて分析した.アクセントのピッチ,最高ピッチ,ピッチレンジなどにおいて,IDSはADSを上回る.また,アクセントの相対的位置が後方にずれる「おそさがり」の現象がIDSにおいてより大きいことが観察された.

理研母子会話コーパス,およびその収録に付随して行った読み上げ課題のデータを用いて,対乳児発話(IDS)と対成人発話(ADS)のピッチについて分析した.アクセントのピッチ,最高ピッチ,ピッチレンジなどにおいて,IDSはADSを上回る.また,アクセントの相対的位置が後方にずれる「おそさがり」の現象がIDSにおいてより大きいことが観察された.

理研母子会話コーパス,およびその収録に付随して行った読み上げ課題のデータを用いて,対乳児発話(IDS)と対成人発話(ADS)のピッチについて分析した.アクセントのピッチ,最高ピッチ,ピッチレンジなどにおいて,IDSはADSを上回る.また,アクセントの相対的位置が後方にずれる「おそさがり」の現象がIDSにおいてより大きいことが観察された.

レキシコン内の系列的な情報と大域的な情報を用い,最小対における対立点の左側環境による検索範囲の縮小を考慮に入れて,日本語の音素ごとの機能負担量を推定するための新たな指標を提案した。さらに音声親密度の段階ごとに単語データベースを区分けし,異なるサイズのレキシコンにおいて音素ごとの機能負担量と出現頻度がどのように分布するかを概観した。その結果,自然類をなすような音素群の中でも分布は極めて不均衡なことがわかった。また,もっとも親密度が高くサイズが小さいレキシコンの場合以外には分布の傾向に大きな変化は見られなかった。構造主義的音韻論において音素は統一性とバランスを保った体系を成すと考えられているが,レキシコンにある単語の偏りのため,音素体系はきわめて不平等にしか利用されていないことがわかった。

アクセント範疇の知覚についてはこれまで様々な実験的研究があるが,ピッチ曲線の傾き,母音の無声化,無声子音といった条件を統一的に扱った研究はなかった.本稿ではこれらに焦点を当て,アクセントをトーンの連鎖として記述する音韻的モデルに基づき,STRAIGHT によるF0再合成刺激を用いた知覚実験を行った.<br>実験の結果,アクセント部のピッチ曲線の傾きは,先行研究の結果と異なりアクセント位置の知覚に影響しないこと,また,母音の無声化だけでなく,無声子音の存在もアクセント範疇の知覚に大きく影響することが分かった.また,アクセント型の対立パターンによって,音韻的モデルで設定した各トーンの役割が異なることも判明した.