Acoustic development of vowels in children´s speech

The paper investigates the developmental change in spectral properties of Cantonese vowels [i u ε ? a] in the speech of pre-adolescent Cantonese-speaking male and female children of the ages ranging from 4 to 12. Results of spectral analysis show that (i) there is a negative correlation between the vowel formant frequencies and age; (ii) the reduction in vowel formant frequencies and F1-F2 planar vowel loop area as a function of age is gradual, where quantum jumps between any successive age groups are not observable; (iii) the age-related developmental change in vowel formant frequencies is non-uniform across different vowel categories, with a larger reduction with age in F1 for the mid vowels [ε ?] than the high vowels [i u] and a smaller reduction with age in F2 for the rounded back vowels [u ?] than the unrounded vowels [i ε a]; (iv) between male and female children the differences in vowel formant frequencies (F1F2) begins to appear at 7 years of age and reach their maximum at 12 years of age; (v) the differences in F1-F2 planar vowel loop area between male and female children of the different age groups do not appear to be significant or correlated with age; and (vi) the close similarities between Cantonese and English pre-adolescent children, male and female, in the developmental data on vowel formant frequencies point to a possible universal development of vowel production.