Development of vowel spaces from age 21 to age 49 in a group of 8 talkers

We describe age-related change in speech during young to middle age adulthood using a new resource for phonetic and sociolinguistic analysis. This resource is based on the “Up” series of documentary films, showing a set of 11 individuals filmed at seven year intervals over a period of 42 years. We analyzed 67 sample utterances (minimum duration = 10 s), containing 4493 vowels produced by eight talkers, with the aim of understanding how vowel spaces change in young and middle-age adulthood, prior to physiological changes often observed in elderly talkers. We measured the first and second formants of each vowel token and analyzed several measures of vowel distribution in F1/F2 space: Euclidean distance from the talker's average F1/F2 (“dispersion”), within-category variability (intra-vowel dispersion), and vowel space area. Area of the vowel space was measured using averages of point vowels (/a/, /ae/, /i/, /u/), as well using the convex hull of all vowels. For some individuals, vowel spaces from age 21 to age 49 come to be more compact, in a manner that has previously been observed in elderly speakers. However, we also find considerable individual variability, with no clear age-related trend across speakers.