Corner vowels in males and females ages 4 to 20 years: Fundamental and F1–F4 formant frequencies

The purpose of this study was to determine the developmental trajectory of the four corner vowels' fundamental frequency (f_o) and the first four formant frequencies (F1–F4), and to assess when speaker-sex differences emerge. Five words per vowel, two of which were produced twice, were analyzed for f_o and estimates of the first four formants frequencies from 190 (97 female, 93 male) typically developing speakers ages 4–20 years old. Findings revealed developmental trajectories with decreasing values of f_o and formant frequencies. Sex differences in f_o emerged at age 7. The decrease of f_o was larger in males than females with a marked drop during puberty. Sex differences in formant frequencies appeared at the earliest age under study and varied with vowel and formant. Generally, the higher formants (F3-F4) were sensitive to sex differences. Inter- and intra-speaker variability declined with age but had somewhat different patterns, likely reflective of maturing motor control that interacts with the changing anatomy. This study reports a source of developmental normative data on f_o and the first four formants in both sexes. The different developmental patterns in the first four formants and vowel-formant interactions in sex differences likely point to anatomic factors, although speech-learning phenomena cannot be discounted.