The Effect of Ageing on Speech Rhythm: A Study on Zurich German

Speech segmental and suprasegmental characteristics vary considerably across the life span, for example, due to degenerative changes in speech production mechanisms and neuro-muscolar control. A great deal of research on the acoustic correlates of adult speakers’ voice has focussed on changes in voice quality, vowel formant patterns, f0, amplitude and speech rate. Only little attention has been paid on speech rhythm variability due to advancing age. Here we quantified age-related rhythmic variability in terms of the durational characteristics of consonantal and vocalic intervals (henceforth CV intervals). We compared the segmental durational variability of two groups of Zurich German speakers. Group 1: 16 young adults, aged from 18 to 32 years; group 2: 10 older adults, aged from 66 to 81 years. For both groups we analyzed 20 sentences in Zurich German from the TEVOID Corpus. Between-speaker durational variability across age was quantified through a variety of interval-based metrics: segment rate, %V, deltaC, deltaV, VarcoC, VarcoV, rPVI-C and nPVI-V. Results showed that rhythmic differences between younger and older adults are largely accountable for by speech rate differences. Segment rate, %V and raw measures of CV interval durational variability (deltaV, deltaC and rPVI-C) showed effects between younger and older adults. Rate normalized metrics (VarcoC, VarcoV and n-PVI-V) did not differ significantly between the two age-groups.