VARIANCE IN CHILDREN'S SPEECH--ACOUSTICS AND PERCEPTION

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Research on the production of stop and nasal consonants in adult speech has shown that these sounds are comprised of acoustic correlates that can be dichotomized into primary invariant properties and secondary variant properties (Cole and Scott, 1974; Stevens and Blumstein, 1981). Although there is evidence from production and perception of adult speech for these properties, little data exist on the role of productive and perceptual invariance and variance in phonological acquisition. The specific aims of this research are to provide acoustic data on stop and nasal consonants in children and to test theories of acoustic and perceptual invariance and variance from a developmental perspective. The perception of children's speech will also be evaluated relative to processes of integration proposed to occur in the perception of adult speech. The significance of this research is that it will provide a basis to examine developmentally theories of invariance and variance by comparing converging evidence from both speech acoustics and perception. To accomplish these aims, eight normal children from each of six age groups, 3, 4, 5, 7, 99, and 11 will record consonant-vowel (CV) syllables comprised of stops /p, t, k, b, d, g/ and nasals /m, n/ each combined with the vowels /i, ae, u, a /. In addition, an adult group of eight subjects will record these stimuli for control purposes. The CV syllables will be analyzed acoustically using LPC and or DFT techniques. Stimulus onsets will be examined relative to invariant templates for labial, alveolar, and velar features. In addition, the following variant properties will be analyzed relative to their characterization of place of articulation in stops and nasals: formant transition onset frequencies, duration of first formant, second and third formant space, loci of formant transitions, and burst frequencies. The perceptual salience for adult listeners of invariant and variant cues for place of articulation in children's speech will be determined by a number of perceptual experiments in which the children's syllables will be digitally edited to preserve various segments. The perceptual salience for child listeners of invariant and variant cues for place of articulation will be determined by experiments employing synthetic speech in which the extent and degree of these properties can be controlled. The level of perceptual integration of these acoustic properties in children's speech for adult listeners will be examined according to a split-channel technique.