Formant frequency development: 15 to 36 months.

Developmental characteristics of formant 1 (F1) and formant 2 (F2) are reported for spontaneous vocalizations produced by four young children. Each child was systematically sampled at between 15 and 36 months of age. Results indicated that both F1 and F2 remained relatively unchanged prior to 24 months of age. Significant decreases in average F1 and F2 occurred between 24 and 36 months. When F1 and F2 values were categorized according to tongue elevation and tongue advancement, the most significant changes were associated with high/back articulations. The pattern of formant frequencies noted in the present group of children appears to reflect developmental changes in vocal tract growth and reconfiguration.