Comfortable effort level revisited.

The purpose of this study was to measure the variability of frequency and intensity of speech, using multiple voice samples obtained over a period of time at a speaker's "comfortable effort level." Variability in vocal output within and across several experimental sessions was assessed from measures of speaking fundamental frequency (SFF) and vocal intensity for utterances repeated three times a day over a 3-day period. Three distinct age groups of men and women-young, middle-aged and elderly-repeated the vowel /a/, read a standard passage, and spoke extemporaneously during each experimental session. Results indicated that variability in SFF and intensity were present across experimental sessions, age groups, gender, and speaking samples. Generally, group means indicated that approximately +/- 1 semitone of variability for SFF and approximately 2 db sound pressure level (SPL) variation in vocal intensity from any one experimental session to the next could be expected; individual variations within any group may reach two semitones and 6 db SPL.