Development differences in vowel duration in open and closed syllables.

Vowel duration in open and closed syllables was investigated in groups of ten normal 5-, 8-, and 10-year-old children, and adults. Productions of three syllables (bee, bead, beet), analyzed acoustically for vowel duration, indicated that for all age groups, mean vowel durations for "bee" and "bead" were significantly different from "beet" but were not different from each other. Developmental effects were noted in mean and variability of vowel duration. In addition, a context effect was observed, with adult-like values for both mean and variability obtained at an earlier age for "beet" than for "bee" and "bead." These results suggest that both phonemic and phonetic factors are important in accounting for developmental changes in mean and variability of vowel duration.