Effect of Phonation Type on Maximum Phonation Time

Maximum phonation time (MPT) is commonly used as an indication of phonatory function. However, MPT varies considerably depending on several factors, for instance, laryngeal valving, ie, the completeness of glottal closure. This parameter is closely related to phonation type, which can vary along the continuum between weak and firm glottal adduction, resulting in an abundant and reduced glottal airflow, respectively, ie, Breathy and Pressed phonation. This investigation analyzes the effects of both phonation type and flow rate on MPT, hypothesizing that Pressed and Breathy phonations produce extremes of MPT variation. Audio and lung volume were recorded in 14 singers experienced in performing different singing genres. They sustained the vowel /a/ as long as they could, after a maximum inhalation, a task repeated in Breathy, Flow, Neutral, and Pressed phonations. Real-time visual feedback of sound level and fundamental frequency was provided by means of the FonaDyn software, helping participants to keep these parameters constant across different degrees of vocal fold adduction. The relationship between flow rate, phonation, and MPT was analyzed using multilevel Bayesian models. Such models offer a better quantification of uncertainty, full probability distributions, and the ability to integrate the results of previous experiments into current analyses as compared to equivalent frequentist models. The results suggested that MPT varies with both flow rate and phonation type: the former is a stronger standalone predictor of MPT than the latter. The implication of such a finding is that, when access to flow data is not available, MPT is still a useful metric, provided that control for phonation type is considered. Indeed, much of the variation of published MPT data may reflect phonation type differences. Thus, future investigations should control for phonation type when MPT data are compared.