Effects of monitoring vocal intensity on oral air flow in children and adults

The purposes of the present investigation were (a) to determine whether child and adult oral air flow data were parallel across two monitoring methods, (b) to determine whether an instruction to speak at a 'comfortable effort level' resulted in greater variability of peak oral air flow (V̇₀) than visual monitoring of vocal intensity level, and (c) to expose possible sources of variation introduced by visual monitoring. Peak V̇₀ from children and adults was measured for stops and fricatives in connected speech during a 'comfortable-effort-level' task and during a visually monitored vocal intensity task. The lack of an age-by-monitoring effect in the analysis of variance (ANOVA) showed that child and adult data were parallel. The nonsignificance of F-Max scores for testing across-subject variability showed that the natural maintenance of a comfortable intensity level did not produce greater V̇₀ variance than visual monitoring. This result was extended by a within-subjects comparison: visual monitoring induced subjects to alter their V̇₀ production for some phonemes. Although the V̇₀ of voiced consonants increased only slightly from comfort-level to visual monitoring, the V̇₀ of voiceless consonants increased more sharply. Thus, visual monitoring does not decrease V̇₀ variability, and does introduce spurious V̇₀ values for some consonants.