Development of speech rhythm in first language: The role of syllable intensity variability.

The opening-closing alternations of the mouth were viewed as the articulatory basis of speech rhythm. Such articulatory cycles have been observed to highly correlate with the intensity curve of the speech signal. Analysis of the intensity variability in English monolingual children and adults revealed that (1) adults showed significantly smaller intensity variability than children, and (2) intensity variability decreased from intermediate-aged children to older children. Maturation of articulatory motor control is likely to be the main reason for the reduced variability in articulatory cycles, and hence smaller intensity variability in adults and older children.