Some acoustic characteristics in the voices of 6- to 10-year-old children and adults: a comparative sex and developmental perspective.

This study is a follow-up investigation of some of the acoustic characteristics reported for a group of twenty 6-, 8- and 10-year-old children's voices (Whiteside SP, Hodgson C. Log Phon Vocol 1999; 24: 6-13) and compares the data of these children with data from a group of nine adults. The acoustic characteristics for both the children and the adults were examined as a function of age and sex. Fundamental frequency (F0) and the standard deviation (SD) of F0 were investigated for the entire duration of a phrase-final vowel. In addition, the first three formant frequencies of the midpoints for the phrase-final vowel were also investigated, with reference to phonetic context. All acoustic parameters were investigated by examining the age, sex and context-determined differences. Results indicated significant age differences for all acoustic parameters investigated, which were characterized by a general decrease in the frequency values of parameters with increasing age. In addition, significant sex differences were found for all parameters, with the females generally having higher formant frequency values than their male peers across all ages. Significant phonetic context differences were only found for the second formant frequency, with formant values being highest for the context "jar" and lowest for the context "bar". No significant interactions were found for age-by-context, sex-by-context or age-by-sex-context comparisons. Relative formant frequency differences were also examined using Fant's Kn factor, by considering sex-, age- and context-linked patterns. The data also provided some evidence for parallel developmental patterns in the different phonetic contexts of a phrase-final vowel. Furthermore, the results showed that there was some evidence of all three types of the aforementioned patterns in addition to phonetic context-determined changes in K2 factor values. The results reported here, therefore, provide further evidence for age- and sex-linked differences in the patterns of development and maturation of the vocal apparatus.