The relationship between speech segment duration and vowel centralization in a group of older speakers

Abstract

This study examined the relationship between average vowel duration and spectral vowel quality across a group of 149 New Zealand English speakers aged 65 to 90 yr. The primary intent was to determine whether participants who had a natural tendency to speak slowly would also produce more spectrally distinct vowel segments. As a secondary aim, this study investigated whether advancing age exhibited a measurable effect on vowel quality and vowel durations within the group. In examining vowel quality, both flexible and static formant extraction points were compared. Two formant measurements, from selected [ɐ:], [ i:], and [ o:] vowels, were extracted from a standard passage and used to calculate two measurements of vowel space area (VSA) for each speaker. Average vowel duration was calculated from segments across the passage. The study found a statistically significant relationship between speakers' average vowel durations and VSA measurements indicating that, on average, speakers with slower speech rates produced more acoustically distinct speech segments. As expected, increases in average vowel duration were found with advancing age. However, speakers' formant values remained unchanged. It is suggested that the use of a habitually slower speaking rate may assist speakers in maintaining acoustically distinct vowels.

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

“…On the other hand, findings from studies on the acoustic and articulatory variability across the age would support the view that the observed age-related rhythmic changes might be due to reasons other than diminished oro-facial strength or neuro-muscular degeneration [30]- [32]. [30], for example, found that older speakers with longer average vowel durations also tended to produce more acoustically distinct vowels.…”

“…[30], for example, found that older speakers with longer average vowel durations also tended to produce more acoustically distinct vowels. From an articulatory viewpoint, there is evidence that the slower speech is not imputable to constrained lip, jaw movements in older adults [31]- [32].…”

The effect of healthy aging on within-speaker rhythmic variability: A case study on Noam Chomsky

“…According to Bilodeau-Mercure and Tremblay (2016), indeed, older adults reduce their speech rate to compensate for the decrease in lip and jaw stiffness when asked to produce speech at fast and very fast rates. From an acoustic point of view, for example, Fletcher and McAuliffe (2015) found that New Zealand English speakers aged over 65 tended to speak with longer average vowel durations as well as to produce more acoustically distinct vowels. Based on this, we might tentatively interpret the reduced segment/ vowel and consonant rate in Chomsky' speech in view of his attempt to keep his pronunciation clear while giving public speeches.…”

Twenty-eight years of vowels: Tracking phonetic variation through young to middle age adulthood

“…Conversely, vowel lengthening does not necessarily entail vowel space expansion (see e.g. Fletcher et al, 2015). Despite the partial independence of vowel duration and articulation, there is a commonly used research strategy which treats changes in duration, vowel space size, and articulatory range as dierent manifestations of a single gradient phenomenon, commonly referred to as phonetic reduction and phonetic enhancement (or strengthening).…”