Control of voice intensity.

This study examined the control of voice intensity using acoustic and aerodynamic recordings. A total of 34 subjects participated half of them with and half without song training, 21 females and 13 males. The subjects produced the syllable sequence /papapa/ while the acoustic signal, the oral air flow, and the oral air pressure were recorded using the Kay-Pentax Phonatory Aerodynamic System. The oral pressure provided an estimate of the subglottal pressure. A measure of glottal flow resistance was calculated as the ratio between subglottal pressure and oral air flow.Three different voice levels were used, normal, reduced, and increased; the change between the normal level and the two others was required to be 6-10 dB. Overall, an increase in voice intensity was associated with increased subglottal pressure and glottal flow resistance with only a small increase in air flow. A comparison between the subjects with and without song training showed those with training to produce higher intensities, to use higher subglottal pressure, but lower glottal flow resistance. Female voices had lower subglottal pressure and lower flow rates but higher glottal resistance than male voices