Abstract
The development of children's ability to produce high versus low vowels and front versus back vowels was examined in a longitudinal study. Acoustic measurements were made of the vowels in spontaneously produced words with known referents. Vowels were grouped by target vowel into high, front (/i/, /i/), high back (/u/, /U/), and low (/ɑ/, /ɔ/). Evidence for control of vowel height was measured in terms of first formant frequency (F1) change over time. Vowel backing was measured by changes in second formant frequency (F2). Average F1 and F2 values and standard deviations of F1 and F2 were detertmined from harmonic amplitudes in narrow‐band discrete Fourier transforms and from local maxima in LPC spectra. Over periods of 5 months, the average F1 for high vowels decreased while the average F1 for low vowels increased. Also, standard deviations for each vowel group decreased with age. Control of backing was seen primarily in increasing average F2 for front vowels. Standard deviations of F2 for both front and back vowels decreased with age. [Work supported by grants from the U. S. Department of Education and from NINCDS.]
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