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S Nittrouer

Publications and source records attributed to S Nittrouer.

26 records · Page 2Linked to original sources
PubMed1989

The perceptual effects of child-adult differences in fricative-vowel coarticulation.

Earlier work [Nittrouer et al., J. Speech Hear. Res. 32, 120-132 (1989)] demonstrated greater evidence of coarticulation in the fricative-vowel syllables of children than in those of adults when measured by anticipatory vowel effects on the resonant frequency of the fricative back cavity. In the present study, three experiments showed that this increased coarticulation led to improved vowel recognition from the fricative noise alone: Vowel identification by adult listeners was better overall for children's productions and was successful earlier in the fricative noise. This enhanced vowel recognition for children's samples was obtained in spite of the fact that children's and adults' samples were randomized together, therefore indicating that listeners were able to normalize the vowel information within a fricative noise where there often was acoustic evidence of only one formant associated primarily with the vowel. Correct vowel judgments were found to be largely independent of fricative identification. However, when another coarticulatory effect, the lowering of the main spectral prominence of the fricative noise for /u/ versus /i/, was taken into account, vowel judgments were found to interact with fricative identification. The results show that listeners are sensitive to the greater coarticulation in children's fricative-vowel syllables, and that, in some circumstances, they do not need to make a correct identification of the most prominently specified phone in order to make a correct identification of a coarticulated one.

Adult↗
PubMed1989

The emergence of phonetic segments: evidence from the spectral structure of fricative-vowel syllables spoken by children and adults.

A variety of evidence, including the speech errors of normal and aphasic speakers, and the metalinguistic skills of literate individuals, demonstrates that speech has an underlying phonemic organization. However, we know little about how this organization develops in the child. The purpose of the present study was to test the hypothesis that phoneme-sized phonetic segments emerge as functional units of perceptuomotor control from the child's gradual reorganization of the gestures forming its early words or syllables. We investigated the acoustic structure of syllables produced by young children and adults. Fricative-vowel syllables spoken by 40 subjects (eight adults and eight children at each of the ages 3, 4, 5, and 7 years) were analyzed acoustically to determine how well different syllables-initial fricatives were contrasted and how strongly they were affected by vocalic context. Results indicated two independent developmental trends: The extent to which speakers differentiated between /integral of/ and /s/ increased with age, while the extent to which they coarticulated each fricative with its following vowel decreased. The results support the hypothesis that children initially organize their speech gestures over a domain at least the size of the syllable and only gradually differentiate the syllable into patterns of gestures more closely aligned with its perceived segmental components.

Adult↗
PubMed1988

Differences in fricative production between children and adults: evidence from an acoustic analysis of /sh/ and /s/.

Speech samples of 12 speakers (8 children and 4 adults) producing the fricatives /s/ and/sh/ followed by the vowels /i/ and /u/ were analyzed to locate the major spectral prominences. Results showed that the fricative low-frequency prominences for children's samples differed from those of adults in three important ways: (1) They were generally higher in frequency; (2) they were greater in amplitude relative to higher frequency regions; and (3) they showed greater effects of vowel context. The first finding can be explained by a simple scaling of adult models of fricative production to accommodate children's smaller vocal tracts. The other two findings suggest, however, that there are other anatomical and articulatory differences between children and adults affecting fricative production. The data presented here suggest that one important difference may be the relative sizes of the fricative constriction and the glottal opening.

Adult↗
PubMed1988

Mathematical treatment of context effects in phoneme and word recognition.

Percent recognition of phonemes and whole syllables, measured in both consonant-vowel-consonant (CVC) words and CVC nonsense syllables, is reported for normal young adults listening at four signal-to-noise (S/N) ratios. Similar data are reported for the recognition of words and whole sentences in three types of sentence: high predictability (HP) sentences, with both semantic and syntactic constraints; low predictability (LP) sentences, with primarily syntactic constraints; and zero predictability (ZP) sentences, with neither semantic nor syntactic constraints. The probability of recognition of speech units in context (pc) is shown to be related to the probability of recognition without context (pi) by the equation pc = 1 - (1-pi)k, where k is a constant. The factor k is interpreted as the amount by which the channels of statistically independent information are effectively multiplied when contextual constraints are added. Empirical values of k are approximately 1.3 and 2.7 for word and sentence context, respectively. In a second analysis, the probability of recognition of wholes (pw) is shown to be related to the probability of recognition of the constituent parts (pp) by the equation pw = pjp, where j represents the effective number of statistically independent parts within a whole. The empirically determined mean values of j for nonsense materials are not significantly different from the number of parts in a whole, as predicted by the underlying theory. In CVC words, the value of j is constant at approximately 2.5. In the four-word HP sentences, it falls from approximately 2.5 to approximately 1.6 as the inherent recognition probability for words falls from 100% to 0%, demonstrating an increasing tendency to perceive HP sentences either as wholes, or not at all, as S/N ratio deteriorates.

Adult↗
PubMed1988

Patterns of interarticulator phasing and their relation to linguistic structure.

Work by Tuller and Kelso [J. Acoust. Soc. Am. 76, 1030-1036 (1984)] and Kelso et al. [J. Phon. 14, 29-59 (1986)] has demonstrated stable relations between jaw and lip movements in (bV#CVb) utterances across rate and stress conditions. Specifically, the onset of lip movement toward the intervocalic consonant was found to be constant with respect to the vowel-to-vowel jaw cycle in both time and relative phasing. An attempt was made to replicate and extend this work by investigating interarticulator phase relations for utterances having a broader range of linguistic organization: In addition to rate and stress, syllable structure (open versus closed syllables) and identity of the intervocalic consonant (/p/ vs /m/) were manipulated. Results showed that the upper lip's lowering onset varied systematically with respect to the jaw vowel cycle as a function of both rate and stress. In addition, syllable structure and consonant identity influenced the relation of lip and jaw gestures. There was a general tendency for any condition that shortened the first vowel to produce earlier onsets of the upper lip relative to the jaw. However, the within-condition jaw cycle duration variability did not correlate with the within-condition variability in phase. Thus it seems that stable interarticulator phase relations maintain not only the integrity of phonological structure, as suggested by Kelso et al., but structural integrity at other levels of linguistic organization as well.

Female↗
PubMed1987

The role of coarticulatory effects in the perception of fricatives by children and adults.

Adult listeners are sensitive to the acoustic variations that result from a speaker's coarticulation (or coproduction) of phonetic segments. The present study charted the development of such sensitivity in young children by examining their responses to coarticulatory effects in fricative-vowel syllables. Children, at each of the ages 3, 4, 5, and 7 years, and adults identified tokens from a synthetic /sh/-/s/ continuum followed by one of four natural vocalic portions: /i/ and /u/, produced with transitions appropriate for either /sh/ or /s/. Children demonstrated larger shifts in fricative phoneme boundaries as a function of vocalic transition than did adults, but relatively smaller shifts as a function of vowel quality. Responses were less consistent for children than for adults, and differences between children and adults decreased as children increased in age. Overall, these results indicate that perceptual sensitivity to certain coarticulatory effects is present at as young as 3 years of age. Moreover, the decrease in the sensitivity to vocalic transitions with age suggests that, contrary to a commonly held view, the perceptual organization of speech may become more rather than less segmental as the child develops.

Adult↗
PubMed1986

The stop-glide distinction: acoustic analysis and perceptual effect of variation in syllable amplitude envelope for initial /b/ and /w/.

Amplitude change at consonantal release has been proposed as an invariant acoustic property distinguishing between the classes of stops and glides [Mack and Blumstein, J. Acoust. Soc. Am. 73, 1739-1750 (1983)]. Following procedures of Mack and Blumstein, we measured the amplitude change in the vicinity of the consonantal release for two speakers. The results for one speaker matched those of Mack and Blumstein, while those for the second speaker showed some differences. In a subsequent experiment, we tested the hypothesis that a difference in amplitude change serves as an invariant perceptual cue for distinguishing between continuants and noncontinuants, and more specifically, as a critical cue for identifying stops and glides [Shinn and Blumstein, J. Acoust. Soc. Am. 75, 1243-1252 (1984)]. Interchanging the amplitude envelopes of natural /bV/ and /wV/ syllables containing the same vowel had little effect on perception: 97% of all syllables were identified as originally produced. Thus, although amplitude change in the vicinity of consonantal release may distinguish acoustically between stops and glides with some consistency, the change is not fully invariant, and certainly does not seem to be a critical perceptual cue in natural speech.

Humans↗