Variations across time in acoustic and electroglottographic measures of phonatory function in women with and without vocal nodules.

The purpose of this investigation was to identify variations over time in phonatory function of women with and without vocal nodules using acoustic and electroglottographic measures. Subjects were 10 women with vocal nodules (mean age = 22.1, range = 19-25) and 10 women with healthy larynges (mean age = 25.0, range = 18-32). Electroglottographic and audio recordings of speech were obtained for each subject over 3 consecutive days at three target times: morning, afternoon, and evening. Estimates of fundamental frequency (Hz), jitter (msec), shimmer (dB), and signal-to-noise ratio (dB) were made from a 1000 msec midportion of the vowel /a/ produced in a carrier phrase. In addition, a closed-to-open ratio was derived from the EGG duty cycle of the same 1000 msec segment and used to estimate timing characteristics of vocal fold vibration. The results showed no significant differences between the groups regarding a pattern of change in the acoustic or the EGG measures across times throughout the day. Furthermore, the experimental group demonstrated significantly lower closed-to-open ratios than the control group. With this exception, no other statistically significant differences between the groups were found.