Harmonics-to-noise ratios in normally speaking prepubescent girls and boys.

This study examined harmonics-to-noise ratios (HNR) in 4 groups of normally speaking children. HNRs were calculated for the vowels /ai/ and /inverted v/, selected from conversational speech samples of 80 children aged 4, 6, 8, and 10 years (10 boys and 10 girls at each age level). HNR values for /inverted v/ were significantly higher than those for /ai/. Significant age differences emerged for /ai/ between ages 4 and 8, and ages 8 and 10. Girls obtained significantly higher HNRs than boys for the /ai/ vowel. Overall, the HNR values for these normally speaking children were lower than those reported for normally speaking adults. These findings suggest that acoustic values for children cannot be validly compared to those for adults, and that the child's gender and age should be taken into account when applying spectral analyses to research and/or clinical situations.