Yukari Hirata

Effects of speaking rate on the vowel length distinction in Japanese

Abstract The issue of acoustic invariance was explored with the question of whether an absolute or relative duration value can be found to reliably classify the Japanese phonemic short and long vowels produced across different speaking rates. The stimuli were Japanese disyllabic non-words (Experiment 1) and real words (Experiment 2). Four native speakers produced these words in a carrier sentence at slow, normal, and fast rates. The duration of accented and unaccented short vowels in CVCV contexts and contrasting long vowels in CVVCV and CVCVV contexts, as well as word duration, was measured. Rate changes affected the duration of long vowels more than short vowels in such a way that the duration difference between short and long vowels was greater for slow than normal, and for normal than fast speech. In contrast with the absolute durations, the ratios of long-to-short vowels and three-mora (CVVCV or CVCVV) to two-mora (CVCV) words were less affected by rate changes. Furthermore, the proportion of the vowel to the total word duration was found to distinguish the two vowel length categories across three rates with high accuracy. The results support the view that “relational” acoustic invariance exists that remains stable across speakers and rates.

Effects of speaking rate on the single/geminate stop distinction in Japanese.

This study addressed an issue in the theory of acoustic invariance. The question was whether an invariant acoustic property exists for distinguishing Japanese single and geminate voiceless stops across rates and speakers. Four native Japanese speakers produced disyllabic words with single and geminate stops (e.g., /kako/ and /kak:o/) spoken in a carrier sentence at three speaking rates. Durations of sentences, words, stop closures, vowels preceding the contrasting stops, and voice onset times were measured. Ratios of geminate to single stop closures, geminate words to singleton words, closures to preceding vowels, and closures to words were calculated. The effect of rate on closure duration was to yield overlap between the singleton and geminate categories, and to lengthen geminate closures more than single closures as rate decreased. However, the ratio of geminate to single closure duration was unaffected by rate. Furthermore, the ratio of closure to word duration (0.35 as an optimal boundary) best classified all singleton and geminate tokens with 95.7%-98% accuracy. Thus, in spite of overlap in absolute closure duration between single and geminate voiceless stops, there is a relationally invariant measure that divides the two phonemic categories across rates and speakers, supporting the theory of relational acoustic invariance. co ustical Society of America.

Effects of speaking rate and vowel length on formant frequency displacement in Japanese.

This study examined effects of phonemic vowel length and speaking rate, two factors that affect vowel duration, on the first and second formants of all vowels in Japanese. The aim was to delineate the aspects of formant displacement that are governed by the physiological proclivity of vowel production shared across languages, and the aspects that reveal language-specific phenomena. Acoustic analysis revealed that the phonemic long vowels occupied a more peripheral portion of the F1 × F2 vowel space than the phonemic short vowels (effect of vowel length), but effects of speaking rate were less clear. This was because of the significant interactions of the two effects: the formants of phonemic short vowels were more affected by speaking rates than the phonemic long vowels. Regression analyses between F2 and duration revealed that formant displacement occurs when vowels are less than 200 ms. Similarities and differences found for Japanese and English are discussed in terms of physiological proclivity of vowel production versus language-specific phonological encoding.

Role of Word-External Contexts in Native Speakers’ Identification of Vowel Length in Japanese

Five groups of native Japanese listeners were assigned to five conditions differing in word-external contexts. In the Intact condition, three types of target disyllables, /mVmV/, /mV:mV/, and /mVmV:/ were spoken in a carrier sentence at two speaking rates. In the other four conditions, the target disyllables of the Intact condition were excised from the original carrier sentence (Excised); embedded in the carrier sentence of the other rate (Mismatch); presented only with the preceding three syllables (Preceding), and presented only with the following three syllables (Following). The accuracy for identifying the word types was higher for the Intact than Excised and Mismatch conditions, indicating that the presence of the carrier sentence with an appropriate rate was important for accurate identification. It was also found that either the preceding or the following short phrase contained sufficient information for identifying the word types. Further, there were effects of the preceding and following phrases on both the first and second vowels of the targets, suggesting that the distant speech materials more than two phonemes away from a target in both sides can affect identification accuracy. Implications are discussed in terms of the adjacency principle for rate normalization.

Effects of Hand Gestures on Auditory Learning of Second-Language Vowel Length Contrasts

PURPOSE Research has shown that hand gestures affect comprehension and production of speech at semantic, syntactic, and pragmatic levels for both native language and second language (L2). This study investigated a relatively less explored question: Do hand gestures influence auditory learning of an L2 at the segmental phonology level? METHOD To examine auditory learning of phonemic vowel length contrasts in Japanese, 88 native English-speaking participants took an auditory test before and after one of the following 4 types of training in which they (a) observed an instructor in a video speaking Japanese words while she made syllabic-rhythm hand gesture, (b) produced this gesture with the instructor, (c) observed the instructor speaking those words and her moraic-rhythm hand gesture, or (d) produced the moraic-rhythm gesture with the instructor. RESULTS All of the training types yielded similar auditory improvement in identifying vowel length contrast. However, observing the syllabic-rhythm hand gesture yielded the most balanced improvement between word-initial and word-final vowels and between slow and fast speaking rates. CONCLUSIONS The overall effect of hand gesture on learning of segmental phonology is limited. Implications for theories of hand gesture are discussed in terms of the role it plays at different linguistic levels.

Exploring the role of hand gestures in learning novel phoneme contrasts and vocabulary in a second language

Co-speech hand gestures are a type of multimodal input that has received relatively little attention in the context of second language learning. The present study explored the role that observing and producing different types of gestures plays in learning novel speech sounds and word meanings in an L2. Naïve English-speakers were taught two components of Japanese—novel phonemic vowel length contrasts and vocabulary items comprised of those contrasts—in one of four different gesture conditions: Syllable Observe, Syllable Produce, Mora Observe, and Mora Produce. Half of the gestures conveyed intuitive information about syllable structure, and the other half, unintuitive information about Japanese mora structure. Within each Syllable and Mora condition, half of the participants only observed the gestures that accompanied speech during training, and the other half also produced the gestures that they observed along with the speech. The main finding was that participants across all four conditions had similar outcomes in two different types of auditory identification tasks and a vocabulary test. The results suggest that hand gestures may not be well suited for learning novel phonetic distinctions at the syllable level within a word, and thus, gesture-speech integration may break down at the lowest levels of language processing and learning.

Production of single and geminate stops in Japanese three- and four-mora wordsa)

This study examined the durational structure of single and geminate stop distinction produced in three- and four-mora words of Japanese, (C(1))V(1)(C(2))C(2)V(2)X [(C(2))C(2) = the contrasting consonants; X = a CV mora, the moraic nasal, or a long vowel as part of V(2)]. The questions addressed were how factors such as speaking rate, segmental variability, and moraic composition of words affected the stop quantity distinction in words longer than well-studied disyllabic words, and whether there exists an invariant parameter that classified these two stop categories. Results showed that all of those factors systematically affected the duration of the contrasting stop closure, the unit of [(C(1))V(1)(C(2))C(2)V(2)], and the entire three- and four-mora words. However, the durational units of moras and words were well-structured, and the ratio of the contrasting stop closure to the [(C(1))V(1)(C(2))C(2)V(2)] unit, as well as the ratio of the closure to the entire word, were found to be invariant in indicating the stop quantity distinction. These results support the theory of relational acoustic invariance [Pickett et al., Phonetica 56, 135-157 (1999)] on the part of production. Furthermore, the results provide insight into different versions of Japanese mora hypothesis [Han, The Study of Sounds 10, 65-80 (1962); Port et al., J. Acoust. Soc. Am. 81(5), 1574-1585 (1987)], which have been under debate for five decades.

Effects of speaking rate on the vowel length distinction in Japanese nonsense words

This study examined how speaking rate affected the durations of phonemic short and long vowels in Japanese. Four native Japanese speakers produced five triplets of disyllabic nonsense words: CVCV, CVVCV, and CVCVV (C=/m/; V=/i/, /e/, /a/, /o/, and /u/), e.g., /mama/, /ma:ma/, and /mama:/. Speakers read these words in a carrier sentence at slow, normal, and fast rates three times each. Durations of accented and unaccented short vowels in CVCV, and contrasting accented long vowels in CVVCV and unaccented long vowels in CVCVV, as well as word durations, were measured from spectrograms. There was a significant amount of overlap between the durations of short and long vowels across the three rates. Rate changes affected the duration of long vowels more than short vowels, showing asymmetry of distribution, consistent with Port et al. [Phonetica 37, 235–252 (1980)]. In contrast with the absolute durations, the ratios of long to short vowels, three‐mora (CVVCV or CVCVV) to two‐mora (CVCV) words, and vowe...

Effects of context and speaking rate on liquid–stop sequences: A reassessment of traditional acoustic cues

The allophonic variation of liquids in American English prompted a study examining the findings of Mann [Percept. Psychophys. 28, 407–412 (1980)], Fowler etal . [Percept. Psychophys. 48, 559–570 (1990)], and Liberman [Speech (1996)], who used the F3 transition as the primary cue for synthesizing [da] vs [ga] following [al] and [ar]. The disyllables /al–da/, /al–ga/, /ar–da/, and /ar–ga/ were recorded in a carrier sentence by two male and two female speakers of midwestern English at three different speaking rates, and the spectra and durations of the liquids, stops, and vowels were analyzed. Acoustic analyses indicate structural variation: The F3 transitions of [da] and [ga] by themselves are not stable correlates in these contexts, notwithstanding data used in arguments for the perceptual invariance of articulatory gestures in liquid–stop sequences. Regularities were also found: The liquids systematically affect the F2 and F3 of the vowel in the following stop–vowel sequence, not only the onset value of F...

Transfer of L1 tone knowledge to L2 vowel quantity contrasts as a secondary cue: The case of Cantonese learners of Japanese

Distinguishing vowel quantities in Japanese is problematic for Cantonese-speaking learners. Vowel length is lexically contrastive in Japanese but not in Cantonese. Apart from duration, fundamental frequency (F0) patterns are secondary cues to vowel length distinction. As tone is lexically contrastive in Cantonese (particularly rising vs. high level), learners would likely be able to transfer this phonological knowledge to help themselves acquire vowel length contrast in Japanese. A perception experiment was conducted in which learners listened to Japanese disyllabic words. The first syllable of which was lengthened according to the within-word vowel duration ratio in eight steps. A level or dynamic (rising or falling) F0 pattern was then imposed on the first vowel. Similar to other L2 learners, Cantonese-speaking learners did not perceive the long vs. short contrast categorically, but gradiently. While both dynamic F0 patterns signal a long vowel, they only exploited the rising pattern to recognise a long...