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

Intraoral air pressure (Po) varies as a function of age. Specifically, children produce significantly higher Po values than adults. The higher Po 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 Po values when sound pressure level (SPL) is held constant. Measurements were made of Po generated by children and adults during a connected speech task completed at three intensity levels. The findings of the study indicated that peak Po values increased as vocal intensity increased for all subject groups, peak Po values were higher for voiceless stops than for voiced stops, and peak Po 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 female, and between adult and child vocal tracts, all groups use the same Po mechanism for achieving a given vocal intensity level.