DEPENDENCE OF PHONATORY EFFORT ON HYDRATION LEVEL

In this study, a double-blind placebo-controlled approach was used to assess the relation between hydration level and phonatory effort. Twel ve adult, untrained voice users with normal voices participated as sub jects. Each subject received a 4-hour hydration treatment, a 4-hour de hydration treatment, and a 4-hour placebo (control) treatment. Followi ng each treatment, phonatory effort was measured with a physiological measure, phonation threshold pressure (PTP), and with a psychological measure, direct magnitude estimation of perceived phonatory effort (DM EPPE). Summarizing the results across these measures, the findings ind icated an inverse relation between phonatory effort and hydration leve l, but primarily for high-pitched phonation tasks. The findings for PT Ps replicated those from an earlier study conducted without double-bli nd experimental manipulations (Verdolini-Marston, Titze, & Druker, 199 0). Theoretical discussion focuses on the possible role of vocal fold tissue viscosity for hydration and dehydration effects, although direc t measures of tissue viscosity are lacking.