AERODYNAMIC AND ELECTROGLOTTOGRAPHIC MEASURES OF NORMAL VOICE PRODUCTION - INTRASUBJECT VARIABILITY WITHIN AND ACROSS SESSIONS

The purpose of this investigation was to quantify the normal intrasubj ect performance variability of four measures of phonatory function wit hin and across sessions. Two different speaking tasks, syllable series and sentence production, were used to determine if more natural speak ing tasks resulted in greater intrasubject variability. Vowel type ([i ] versus [alpha]) also was varied. Estimated subglottal air pressure, mean phonatory air flow, abduction quotient, and fundamental frequency were derived from aerodynamic and electroglottographic signals obtain ed from 11 normally speaking men and 10 normally speaking women on fou r different days. Relative intrasubject variability was compared acros s speaking task, gender, and vowel type. Average across-session intras ubject variability was 5% for fundamental frequency and abduction quot ient, 8% for estimated subglottal air pressure, and 15% for mean phona tory air flow during syllable repetition. There was significantly grea ter intrasubject variability for mean phonatory air flow and abduction quotient for the sentence repetition task. There were no significant differences in intrasubject variability across gender and vowel type. The data were used to compute cutoff values that represent the amount of variability that would be considered within normal limits. These no rmal data can be used for comparison when assessing and monitoring the phonatory abilities of individuals with voice disorders.