Abstract
Speech rhythm varies noticeably from language to language, and within the same language as a function of numerous linguistic, prosodic and speaker-dependent factors, among which is the speaker’s age. 
Cross-sectional studies comparing the acoustic characteristics of young and old voices have documented that healthy aging affects speech rhythm variability. This kind of studies, however, presents one fundamental limitation: They group together people with different life experiences, healthy conditions and aging rate. This makes it very difficult to disentangle the effect of aging from that of other factors when interpreting the rhythmic differences between younger and older adults.
In the present paper, we overcame such difficulty by tracing rhythmic variability within one single individual longitudinally. We examined 5 public talks held by Noam Chomsky, from when he was 40 to when he was 89. Within-speaker rhythmic variability was quantified through a variety of rate measures (segment/consonant and vowel rate) and rhythmic metrics (%V, %Vn, nPVI-V, n-PVI-C). The results showed that physiological aging affected speech rate measures, but not the durational characteristics of vocalic and consonantal intervals. More longitudinal data from numerous speakers of the same language are necessary to identify generalizable patterns in age-related rhythmic variability.
Pellegrino, Elisa