Relationship between intraoral air pressure and vocal intensity in children and adults

Intraoral air pressure (P₀) varies as a function of age. Specifically, children produce significantly higher P₀ values than adults. The higher P₀ produced by children has been discussed in relation to age-related volumetric differences of the subglottal and vocal tract, to lung compression differences, and to the fact that children's 'comfortable' speaking level might exceed that of adults. The present study was undertaken to evaluate the hypothesis that children (vs. adults) and women (vs. men) produce higher P₀ values when sound pressure level (SPL) is held constant. Measurements were made of P₀ generated by children and adults during a connected speech task completed at three intensity levels. The findings of the study indicated that (a) peak P₀ values increased as vocal intensity increased for all subject groups, (b) peak p₀ values were higher for voiceless stops than for voiced stops, and (c) peak P₀ values were not significantly different for adults than for children or for men than for women. These results were interpreted to show that despite physical and physiological differences between male and females, and between adult and child vocal tracts, all groups use the same P₀ mechanism for achieving a given vocal intensity level.