An exploratory model of speech intelligibility for healthy aging based on phonatory and articulatory measures

Abstract Purpose The aims of the current study were to determine age-related changes to the phonatory and articulatory subsystems and to investigate an exploratory model of intelligibility for healthy aging based on phonatory and articulatory measures. Method Fifteen healthy, older adults (55-81 years) and 15 younger adults (20-35 years) participated in instrumental assessments of the phonatory (aerodynamic, acoustic) and articulatory (kinematic) subsystems. Speech intelligibility was determined by five listeners during multi-talker babble. Results Older adults displayed shorter maximum phonation time, greater airflow during sentence reading, and lower cepstral peak prominence (CPP) and CPP SD. Additionally, older adults had slower tongue movement speed than younger adults. Speech intelligibility was also significantly reduced in the older group. A generalized estimating equations model combining phonatory and articulatory measures showed that CPP SD, low/high (L/H) spectral ratio mean and SD, Cepstral Spectral Index of Dysphonia (CSID), and maximum tongue movement speed were significant contributors to intelligibility changes in older individuals. While L/H mean and SD and CSID displayed an inverse relationship with intelligibility, CPP SD and maximum tongue speed displayed a direct relationship with intelligibility. Discussion Aging affects the phonatory and articulatory subsystems with implications for speech intelligibility. Phonatory cepstral/spectral measures except for mean CPP were associated with speech intelligibility changes, suggesting that changes in voice quality may contribute to reduced intelligibility in older adults. Pertaining to articulation, slower tongue movement speed likely contributed to reduced intelligibility in older individuals.