Volume 119, Issue 3, March 2006
Index of content:
- SPEECH PERCEPTION 
Perception of the [m]-[n] distinction in consonant-vowel (CV) and vowel-consonant (VC) syllables produced by child and adult talkers119(2006); http://dx.doi.org/10.1121/1.2140830View Description Hide Description
The contribution of the nasal murmur and vocalic formant transition to the perception of the [m]-[n] distinction by adult listeners was investigated for speakers of different ages in both consonant-vowel (CV) and vowel-consonant (VC) syllables. Three children in each of the speaker groups 3, 5, and old, and three adult females and three adult males produced CV and VC syllables consisting of either [m] or [n] and followed or preceded by [i æ u a], respectively. Two productions of each syllable were edited into seven murmur and transitions segments. Across speaker groups, a segment including the last of the murmur and the first of the vowel yielded higher perceptual identification of place of articulation than any other segment edited from the CV syllable. In contrast, the corresponding segment in the VC syllable position improved nasal identification relative to other segment types for only the adult talkers. Overall, the CV syllable was perceptually more distinctive than the VC syllable, but this distinctiveness interacted with speaker group and stimulus duration. As predicted by previous studies and the current results of perceptual testing, acoustic analyses of adult syllable productions showed systematic differences between labial and alveolar places of articulation, but these differences were only marginally observed in the youngest children’s speech. Also predicted by the current perceptual results, these acoustic properties differentiating place of articulation of nasal consonants were reliably different for CV syllables compared to VC syllables. A series of comparisons of perceptual data across speaker groups, segment types, and syllable shape provided strong support, in adult speakers, for the “discontinuity hypothesis” [K. N. Stevens, in Phonetic Linguistics: Essays in Honor of Peter Ladefoged, edited by V. A.Fromkin (Academic, London, 1985), pp. 243–255], according to which spectral discontinuities at acoustic boundaries provide critical cues to the perception of place of articulation. In child speakers, the perceptual support for the “discontinuity hypothesis” was weaker and the results indicative of developmental changes in speech production.
119(2006); http://dx.doi.org/10.1121/1.2149768View Description Hide Description
The present study explores the use of extrinsic context in perceptual normalization for the purpose of identifying lexical tones in Cantonese. In each of four experiments, listeners were presented with a target word embedded in a semantically neutral sentential context. The target word was produced with a mid level tone and it was never modified throughout the study, but on any given trial the fundamental frequency of part or all of the context sentence was raised or lowered to varying degrees. The effect of perceptual normalization of tone was quantified as the proportion of non-mid level responses given in F0-shifted contexts. Results showed that listeners’ tonal judgments (i) were proportional to the degree of frequency shift, (ii) were not affected by non-pitch-related differences in talker, (iii) and were affected by the frequency of both the preceding and following context, although (iv) following context affected tonal decisions more strongly than did preceding context. These findings suggest that perceptual normalization of lexical tone may involve a “moving window” or “running average” type of mechanism, that selectively weights more recent pitch information over older information, but does not depend on the perception of a single voice.
119(2006); http://dx.doi.org/10.1121/1.2161431View Description Hide Description
Three experiments tested the hypothesis that vowels play a disproportionate role in hearing talker identity, while consonants are more important in perceiving word meaning. In each study, listeners heard 128 stimuli consisting of two different words. Stimuli were balanced for same/different meaning, same/different talker, and male/female talker. The first word in each was intact, while the second was either intact (Experiment 1), or had vowels (“Consonants-Only”) or consonants (“Vowels-Only”) replaced by silence (Experiments 2, 3). Different listeners performed a same/different judgment of either talker identity (Talker) or word meaning (Meaning). Baseline testing in Experiment 1 showed above-chance performance in both, with greater accuracy for Meaning. In Experiment 2, Talker identity was more accurately judged from Vowels-Only stimuli, with modestly better overall Meaning performance with Consonants-Only stimuli. However, performance with vowel-initial Vowels-Only stimuli in particular was most accurate of all. Editing Vowels-Only stimuli further in Experiment 3 had no effect on Talker discrimination, while dramatically reducing accuracy in the Meaning condition, including both vowel-initial and consonant-initial Vowels-Only stimuli. Overall, results confirmed a priori predictions, but are largely inconsistent with recent tests of vowels and consonants in sentence comprehension. These discrepancies and possible implications for the evolutionary origins of speech are discussed.
119(2006); http://dx.doi.org/10.1121/1.2166611View Description Hide Description
This study assessed the extent to which second-language learners are sensitive to phoneticinformation contained in visual cues when identifying a non-native phonemic contrast. In experiment 1, Spanish and Japanese learners of English were tested on their perception of a labial∕labiodental consonant contrast in audio , visual , and audio-visual modalities. Spanish students showed better performance overall, and much greater sensitivity to visual cues than Japanese students. Both learner groups achieved higher scores in the than in the test condition, thus showing evidence of audio-visual benefit. Experiment 2 examined the perception of the less visually-salient ∕l∕-∕r∕ contrast in Japanese and Korean learners of English. Korean learners obtained much higher scores in auditory and audio-visual conditions than in the visual condition, while Japanese learners generally performed poorly in both modalities. Neither group showed evidence of audio-visual benefit. These results show the impact of the language background of the learner and visual salience of the contrast on the use of visual cues for a non-native contrast. Significant correlations between scores in the auditory and visual conditions suggest that increasing auditory proficiency in identifying a non-native contrast is linked with an increasing proficiency in using visual cues to the contrast.
The effects of hearing loss on the contribution of high- and low-frequency speech information to speech understanding. II. Sloping hearing lossa)119(2006); http://dx.doi.org/10.1121/1.2161432View Description Hide Description
The speech understanding of persons with sloping high-frequency (HF) hearing impairment (HI) was compared to normal hearing (NH) controls and previous research on persons with “flat” losses [Hornsby and Ricketts (2003). J. Acoust. Soc. Am.113, 1706–1717] to examine how hearing loss configuration affects the contribution of speech information in various frequency regions. Speech understanding was assessed at multiple low- and high-pass filter cutoff frequencies. Crossover frequencies, defined as the cutoff frequencies at which low- and high-pass filtering yielded equivalent performance, were significantly lower for the sloping HI, compared to NH, group suggesting that HF HI limits the utility of HF speech information. Speech intelligibility index calculations suggest this limited utility was not due simply to reduced audibility but also to the negative effects of high presentation levels and a poorer-than-normal use of speech information in the frequency region with the greatest hearing loss (the HF regions). This deficit was comparable, however, to that seen in low-frequency regions of persons with similar HF thresholds and “flat” hearing losses suggesting that sensorineural HI results in a “uniform,” rather than frequency-specific, deficit in speech understanding, at least for persons with HF thresholds up to HL.