Using the perturbation of the contact quotient of the EGG waveform to analyze age differences in adult speech.

This study examines electroglottographic (EGG) recordings for 15 young and 14 old male speakers of New Zealand English. Analysis was performed on the sustained vowels /i:/ and /a:/ at three target levels for both pitch and loudness. Jitter was greater for older speakers, and the contact quotient (Qx) was significantly lower for older speakers. The greater jitter for older speakers indicates a decrease in the stability of the vocal production mechanism of the older speakers. The jitter is an acoustic measure, so to examine the stability at a physiological level, a perturbation measure of the Qx is developed and applied to the EGG recordings. The contact quotient perturbation (CQP) showed a significant increase for older speakers (1.55% and 3.54% for young and old, respectively), and this demonstrated more about the variability than the jitter data alone. When loudness is also considered, the Qx was significantly greater for louder vowels, whereas its perturbation was significantly lower for louder vowels. This relationship combined with the age effect, with the CQP for all three loudness levels being greater for the older speakers. The findings of this study will contribute to the development of vocal fold models that account for aging.