Kaori Idemaru

Acoustic covariants of length contrast in Japanese stops

This study explores acoustic correlates to the singleton vs. geminate stop length contrast in Japanese. The proposal examined is that multiple acoustic features covary with the stop length distinction and that these features are available in the signal as potential secondary cues. The results support the proposal, revealing the presence of several acoustic features covarying with the singleton vs. geminate contrast in both durational and non-durational domains. Specifically, the preceding vowel is longer, the following vowel is shorter, there are greater fundamental frequency and intensity changes from the preceding to the following vowel, and there is evidence of more creakiness in voice quality for geminate than singleton consonants. It is also demonstrated that the vowel durations, as well as fundamental frequency and intensity changes have fairly strong categorization power.

Individual differences in cue weights are stable across time: the case of Japanese stop lengths.

Speech categories are defined by multiple acoustic dimensions, and listeners give differential weighting to dimensions in phonetic categorization. The informativeness (predictive strength) of dimensions for categorization is considered an important factor in determining perceptual weighting. However, it is unknown how the perceptual system weighs acoustic dimensions with similar informativeness. This study investigates perceptual weighting of two acoustic dimensions with similar informativeness, exploiting the absolute and relative durations that are nearly equivalent in signaling Japanese singleton and geminate stop categories. In the perception experiments, listeners showed strong individual differences in their perceptual weighting of absolute and relative durations. Furthermore, these individual patterns were stable over repeated testing across as long as 2 months and were resistant to perturbation through short-term manipulation of speech input. Listeners own speech productions were not predictive of how they weighted relative and absolute duration. Despite the theoretical advantage of relative (as opposed to absolute) duration cues across contexts, relative cues are not utilized by all listeners. Moreover, examination of individual differences in cue weighting is a useful tool in exposing the complex relationship between perceptual cue weighting and language regularities.

The developmental trajectory of children's perception and production of English /r/-/l/.

The English /l-r/ distinction is difficult to learn for some second language learners as well as for native-speaking children. This study examines the use of the second (F2) and third (F3) formants in the production and perception of /l/ and /r/ sounds in 4-, 4.5-, 5.5-, and 8.5-yr-old English-speaking children. The children were tested with elicitation and repetition tasks as well as word recognition tasks. The results indicate that whereas young childrens /l/ and /r/ in both production and perception show fairly high accuracy and were well defined along the primary acoustic parameter that differentiates them, F3 frequency, these children were still developing in regard to the integration of the secondary cue, F2 frequency. The pattern of development is consistent with the distribution of these features in the ambient input relative to the /l/ and /r/ category distinction: F3 is robust and reliable, whereas F2 is less reliable in distinguishing /l/ and /r/. With delayed development of F2, cue weighting of F3 and F2 for the English /l-r/ categorization seems to continue to develop beyond 8 or 9 yr of age. These data are consistent with a rather long trajectory of phonetic development whereby native categories are refined and tuned well into childhood.

An acoustic and perceptual investigation of the geminate and singleton stop contrast in Japanese

Segmental durations are known to be heavily influenced by changes in speech rate such that the durations of members of two contrasting length categories may overlap [Pickett et al. ‘‘Effects of speaking rate on singleton/geminate contrast in Italian,’’ Phonetica 56, 135–157 (1999); Hirata & Whiton, ‘‘Relational acoustic invariance in the single/geminate stop distinction in Japanese,’’ J. Acoust. Soc. Am. 117, 2569 (2005)]. Given this, questions arise as to how category distinction is achieved for contrasts signaled by differences in segmental duration. This study investigates the question by examining the production and perception of the Japanese singleton versus geminate stop contrast by adult native speakers. Six native Japanese speakers produced disyllabic words with medial singleton and geminate stops at three speaking rates. Duration of stop closure and a number of relational timings between the closure duration and other segments were examined as potential rate‐independent measures distinguishing th...

Retuning speech sound categories: An eyetracking study.

Speech categories are defined by multiple probabilistic acoustic cues. Fundamental frequency (F0) and voice onset time (VOT) are correlated in the English stop voicing contrast, for example. However, such correlations are often imperfect—especially in cases of non‐native or disordered speech. The present experiments investigate listeners’ ability to adjust perceptual cue weighting in online perception in response to changes in the cue correlations experienced across time. Native‐English listeners heard minimal‐pair words beginning with stop consonants varying along a VOT series. The F0 of the words was gradually shifted over the course of the experiment from the canonical English correlation (higher F0 for voiceless stops) to the opposite pattern (lower F0 for voiceless stops). Categorization was assessed via explicit responses while eye gaze data were simultaneously recorded using the visual world paradigm. Both data types revealed that the influence of F0 on voicing categorization changed in response to...

Perceiving politeness from speech acoustics alone: A cross-linguistic study on Korean and English

Politeness is a crucial aspect of everyday speech communication; however, there are to date only few acoustic studies on this topic. Winter and Grawunder (2012) showed that for Korean speakers, politeness is reflected in pitch, intensity, voice quality and speaking rate. Here, we extend this production study by investigating whether Korean and English listeners can perceive the intended politeness of short Korean utterances based on speech acoustics alone. In two experiments with a total of 47 English and 30 Korean listeners, we found that both groups can detect the intended politeness purely based on the phonetic qualities of speech. In one experiment, accuracy was low (Korean: 58%, English: 53%) because speakers heard multiple voices in a randomized fashion, not allowing them to familiarize with any particular voice. In a design that was blocked by speaker voice, accuracy was higher (Korean: 70%, English: 58%), showing that vocal politeness can be used as a cue when the voice is known. This shows that p...

Foreign accent production and perception: An acoustic analysis of non-native Japanese

What are the characteristics of non-native speech and what contributes to the perception of foreign accent by native speakers? In this study, two experiments are conducted to characterize the acoustic features of non-native Japanese production and to examine how these non-native features influence native Japanese perception of foreign accent. In the production experiment, stop consonants and vowel formants were compared between native Japanese speakers and English speakers with 2 and 4 yr of Japanese instruction. The second experiment examines native listener judgments of foreign accent using a visual analog scale. Preliminary analysis reveals that in both stop consonant and vowel production, learners vary considerably from native speakers, specifically in the production of /k/ and /t/ voice onset time, F1 of /e/, and F2 of /u/ and /i/. These features are correlated with judgment ratings by native Japanese listeners. The findings reveal that even after significant experience in the L2 classroom, speakers ...

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.

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.

Comparative analysis of South Korean and North Korean vowels: A pilot study

This study investigates cardinal vowels of standard North Korean and South Korean. Prior reports have suggested that North and South Korean vowels have undergone changes after decades of relative isolation. This poster reports a pilot study investigating the ways in which the language standards of North and South Korea are similar and different by examining the speech of newscasters from each country. Acoustic analysis of the speech data suggested that North Korean vowels [ɛ] and [ae] were produced in the higher position relative to the South Korean counterparts, and the back vowels [ʌ] and [o] showed overlapping formant values unlike the South Korean counterparts. The perception experiment suggested that South Korean listeners could not accurately identify the North Korean [ʌ] and [o]. These results indicate that there may be interesting differences across North Korean and South Korean vowels.