The purpose of this experiment was to determine whether age-related differences would be observed for identification and discrimination of synthesized, five-formant CV syllables among listeners who showed equal performance scores on a standard clinical test of speech understanding. A second question concerned the relations between performance on identification and discrimination tasks as a function of age. Two 13-item continua that varied in the place of articulation feature ([ba, da, ga]) were used; they differed primarily in the presence of absence of a 5-ms noise burst at the consonant onset. Digitized natural speech syllables were also employed in one experimental task. Strong age effects were obtained for the three tasks--identification of syllables, adaptive estimation of "ba, da-" and "da, ga-" boundaries, and discrimination. With the exception of one condition for six-year-olds, only adults showed significant differences between boundaries and just noticeable differences. Minimal differences were obtained in responses to stimuli with and without initial bursts. Across ages there were no significant differences in the subjects' ability to label the synthesized syllables as compared to the natural speech stimuli. Possible explanations for the observed developmental effects are discussed.

Detection and identification thresholds were obtained for 6-and lO-year-old normal children and normal adults using five-formant synthesized consonant-vowel ([ba]-[da]-[ga)l stimuli. Sixyear-old children were found to have poorer detection than adults, just as they do for pure tones. For the identification task, the slopes of the performance-intensity functions were more shallow for 6-year-old children than for lO-year-olds and adults. Consequently, compared with lO-yearolds and adults, 6-year-old listeners require a greater increase in stimulus intensity above detection threshold to identify these stimuli at a high performance level. The influence of acoustic characteristics of the stimuli on all listeners is also discussed.It has been reported that young children have poorer pure tone sensitivity than adults (e.g

Adaptive test procedures were used to estimate: (1) boundaries between perceptual “categories” of a labeling, or identification, task and (2) the just-discriminable difference to each side of the midpoint of a 13-item /ba/-/da/-/ga/ continuum of 4-formant, synthesized syllables (AX task). At the locus of the /ba/-/da/ boundary: (1) both 10-year olds and adults had significantly better discrimination than 6-year olds; (2) 10-year-olds' categorical boundaries were significantly different from those of 6-year olds; and (3) only adults showed a significant difference between the discrimination limen and the boundary between “categories.” At the locus of the /da/-/ga/ boundary, performance of 6-year-olds differed significantly from adults'. These results were obtained even though all Ss scored approximately 100% correct on a speech discrimination test—WIPI for children and W-22 for adults—and parallel results obtained on a monosyllabic word perception task [Elliott, L. L. et al., J. Acoust. Soc. Am. 66, 12–21 (1979)]. [Supported in part by BEH, NINCDS, and NSF.]

This study compared four measures to equate speech signals for loudness: VU level, A-weighted sound level, sones computed via Stevens' Mark VI, and sones via Zwicker (ISO, R532-1966). Monosyllabic speech tokens were equated for loudness and for indicated magnitude to a stationary reference, a synthesized [a]. Equal loudness was determined with normal listeners in sound field at two levels. Attenuation of each monosyllable was varied until its indicated magnitude (as measured electrically or via digital computation) equaled that of the reference. Attenuation for equal loudness was compared to attenuation for equal indicated magnitude. Results from fast and slow time constants were highly correlated. Presentation level did not alter relative ranking of the indicators. The VU meter performed best in equating speech to the reference; average error was less than the range described by the 95% confidence limits of the loudness judgments (+/−1 dB). Stevens' and Zwicker's procedures performed best in equating loudness among speech signals with an average error of less than 2 dB.

This study investigated the detection and identification of synthesized CV syllables [bɑ, dɑ, gɑ] by 6- and 10-year-old children and adults. Detection thresholds were measured using a three-interval forced-choice, adaptive procedure, with trial-by-trial feedback. Syllable identification was measured using a three-alternative forced-choice task, also with trial-by-trial feedback. Performance-intensity functions for the syllable identification data were fit with a logistic function to determine slope and identification thresholds. Detection thresholds and identification thresholds were significantly poorer for 6-year olds than for 10-year olds and adults; performance-intensity function slopes were significantly more shallow for 6-year olds than for the other groups. The effect of syllable was significant for identification threshold and slope, but not for detection threshold. These results extend previous demonstrations of developmental differences in pure tone sensitivity and word identification to CV syllables. [Work supported, in part, by NSF.]