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Age-Related Changes in Fundamental Frequency and Formants: A Longitudinal Study

This study examines age-related changes in vowel quality and fundamental frequency in four speakers over a long period of time. The results contribute to our understanding of how physiological processes and sound changes in a speech community affect vocal tract maturation.

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Age-Related Changes in Fundamental Frequency and Formants: A Longitudinal Study

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  1. Age-related changes in fundamental frequency and formants: a longitudinal study of four speakers. Jonathan Harrington1, Sallyanne Palethorpe 2, Catherine I. Watson3 1. Institute of Phonetics and Speech Processing (IPS), University of Munich, Munich, Germany. 2 Macquarie Centre for Cognitive Science (MACCS), Macquarie University, Sydney, Australia. 3 Dept. of Electrical and Computing Engineering, The University of Auckland, New Zealand.

  2. Motivation for the present study: sound change and age Vowel quality in adults – even those who live all their lives in the same speech community – changes in time. Some changes are due to phonetic sound changes in the community – e.g. an analysis (Harrington et al, 2000, 2007) of the Queen's Christmas Broadcasts shows a fronter /u/ (GOOSE) and lower /a/ (TRAP) which have both been shown to be sound changes taking place in the standard accent of English. 1. But some vowel quality changes in adulthood are caused by physiological processes of vocal tract maturation and there is certainly extensive evidence that age can be estimated perceptually (e.g., Jacques & Rastatter, 1990; Huntley, Hollien, & Shipp, 1987; Neiman & Applegate, 1990; Ptacek & Sander,1966) 2. Therefore in order to understand 1. we must be able to normalise for 2. (see also Price 2006, Aus. Speech Science & Technology Conference, for a similar analysis/arguments w.r.t. Australian English)

  3. Almost all studies of the acoustic consequences of the aging vocal tract are based on cross-speaker 'apparent time' young vs. old comparisons which may be confounded with other speaker-specific attributes. Perhaps for this reason, the results on age-related changes esp. concerning formant changes are mixed and not well understood physiologically… Motivation: longitudinal study Verdonck-de Leeuw and Mahieu, 2004, Journal of Voice 'Longitudinal studies on vocal aging are scarce..'

  4. Age and f0 But contrary to 2: f0 lowers in males from middle to old age (DeCoster & Debruyne, 1997) Contrary to 1: mean f0 is not a reliable cue for age (Harnsberger et al, 2006) scarcely any change in mean f0 with increasing age in men or women. (e.g Benjamin, 1981; Ramig & Ringel, 1983). 1. Many studies show a correlation between increasing age and decreasing fundamental frequency (Helfrich, 1979; Decoster & Debruyne, 2000;Linville, 2001; Linville & Fisher, 1985) although there is disagreement on whether this applies equally to men and women. 2. Physiological interpretation (e.g. Linville, 2004): "10-15 Hz drop in women at menopause resulting from hormonal changes that cause thickening of the laryngeal mucosa. In men, f0 lowers approximately 10 Hz from young adulthood to middle age…After middle age, f0 in men rises substantially (approximately 35 Hz) into advanced old age, reaching the highest level of adulthood."

  5. Physiological interpretation Laver & Trudgill (1979): the entire respiratory system and digestive tract are in a lower position with increasing age. Such a lowering would cause the vocal tract to lengthen… Linville (2004): Lowering of formant frequencies (more pronounced in women) suggests lengthening of the vocal tract [which] may result from growth of the craniofacial skeleton, lowering of the larynx in the neck… Age and formants Formant lowering with increasing age: Linville & Fisher, 1985, Xue & Hao 2003; Watson & Munson, 2007

  6. Age and formants On the other hand, with increasing age: Xue & Hao (2003) report only oral but not pharyngeal tract lengthening and changes predominantly to F1. Meurer et al (2004) less variation but no formant change Rastatter et al. (1997) found consistent lowering only in F1; and different changes in men and women. Age-related formant changes are vowel specific (Rastatter et al, 1997; Watson & Munson, 2007) Labov’s (1994) analysis of the same person aged 68 and then 85: no evidence of any significant long-term change to F1 or F2 over these years.

  7. Method: Speakers Queen Elizabeth II b. 1926, (accent = RP/U-RP), Christmas broadcasts Years analysed: 1952-1972, 1983, 1985, 1988, 1994-2002. Broadcasts each 5-10 minutes. Alistair Cooke b. 1908, 'Letter from America' (accent = RP with N. American influences). Years analysed = 1947, 1951, 1953, 1960, 1962, 1965, 1970-74, 1980-1985, 1990-2003. Roughly 10 minutes per broadcast. Donald Bradman b. 1908 (accent = Aus.Engl), Two radio interviews in 1948 and 1987 each 20-25 minutes. Margaret Lockwood. b 1916: (accent = RP), two radio interviews, 1951 (5.5 minutes) and 1980 (12.0 minutes) Roy Plomley: b. 1914, (accent = RP) BBC presenter: data from two recordings from 1951 and 1985 Edmund Hillary: b. 1919, (Accent = New Zealand Engl.), two radio interviews 1955 (14 mins), 1992 (14 mins). Two speakers: data from several years over roughly a 50 year period Four speakers data from two years 30-40 years apart.

  8. Method Motivation for choosing schwa: we wish to analyse non-phonetic sound change and as far as we know there is no evidence that schwa (or indeed mean f0 and formants across all voiced frames) have shifted diachronically in the last 60 years in any of the accents analysed. Schwas that were analysed: only those in polysyllabic content words realised as a weak vowel (2nd syll. of 'sofa') but excluding those than can be produced as [I] (i.e., not the 2nd syllable of 'roses'). We report results on mean f0 and mean F1-F3 (a) in schwa vowels (b) across all periodically voiced frames Since we obtained a very similar pattern of results from (a) and (b), we present only the results from (b) here.

  9. C C P P B B H H L L Q Q Results I: Mean f0 and mean F1 in 6 speakers. Mean f0 and F1 from early (in the 1940s/1950s vs. late (1980s/1990s) broadcasts in all 6 speakers. mean f0 mean F1 early 500 200 late 300 Frequency (Hz) 100 50 100 0 0 (Speakers from L to R: Cooke, Plomley, Bradman, Hillary, Lockwood, Queen) f0 is significantly lower in later broadcasts F1 is significantly lower in later broadcasts.

  10. Results II: F2 and F3 Mean F2 and F3 from early (in the 1940s/1950s vs. late (1980s/1990s) broadcasts in all 6 speakers. F3 F2 1.8 2.8 early 1.6 2.6 Frequency (kHz) 1.4 2.4 late 1.2 2.2 C P B H L Q C P B H L Q (Speakers from L to R: Cooke, Plomley, Bradman, Hillary, Lockwood, Queen) No consistent or significant effect across the 6 speakers on average F2 nor average F3 from early to later broadcasts

  11. Results III: f0 and F1 averaged separately by year over a 50 year period in the Queen and Alistair Cooke R2: 0.7768 R2 = 0.6723 50 50 50 50 60 60 60 60 70 70 70 70 80 80 80 80 90 90 90 90 00 00 f0 rises again in very old age R2: 0.723 R2 = 0.7722 We found that these data could be modelled with an exponential of the form 50 50 60 60 70 70 70 70 80 80 80 80 90 90 90 90 00 00 (separately for F = f0 and F = F1) Hz Hz f0 F1 550 550 280 280 Queen 500 500 Frequency 240 240 450 450 200 200 400 400 Hz Hz 130 130 400 400 Cooke 120 120 Frequency 360 360 110 110 320 320 100 100 Decade

  12. Do f0 and F1 decrease at a similar rate? If so, then either r in the exponential regressions for f0 and F1 or equivalently, the slope, log(r), of the straight line in the corresponding log domain should be the same.

  13. 6.0 6.0 5.5 5.8 5.0 5.6 5.4 50 60 70 80 50 60 70 80 90 00 Therefore f0 and F1 decay exponentially in time with increasing age at about the same rate. Do f0 and F1 decrease at a similar rate? Queen Cooke F1 Log frequency f0 Decade F-tests showed that there is no significant difference between the slopes for F1 and f0 (between the red and black line slopes), in the log frequency domain, neither for the Queen, nor for Cooke.

  14. Results IV: F2 and F3 averaged separately by year over a 50 year period in the Queen and Alistair Cooke F2 F3 2.9 1.8 Queen 2.8 1.7 Frequency (kHz) 50 70 90 50 70 90 2.60 Cooke 1.50 2.55 1.46 2.50 Decade 50 60 70 80 90 50 60 70 80 90 No significant linear or exponential trend in F2 or F3 as a function of year for either the Queen or Cooke.

  15. Summary of results Between the age of: % decrease in f0 % decrease in F1 Cooke 42-82 12 26 Plomley 37-71 7 23 Bradman 40-79 25 21 Hillary 36-73 18 16 Lockwood 35-64 25 17 Queen 27-69 20 19 f0 and F1 decay exponentially at about the same rate for both speakers (up to the age of 80 in Cooke) f0 begins to rise in Cooke after the age of 80 (a) across two years (b) approx. every other year over a 50 year period in two speakers (Cooke, Queen) No consistent effects in F2 nor F3 in either (a) or (b)

  16. Interpretations: age and vocal/oral tract lengthening log f0 x log F1 for Cooke between the age of 82 and 94 years 92 94 93 5.80 84 5.75 85 R2 = 0.52, p < 0.001) log F1 90 5.70 91 83 89 5.65 88 86 82 log f0 4.60 4.65 4.70 4.75 It seems unlikely that the vocal tract lengthens with increasing age, given the lack of consistent effects in F2 and F3. Also, when in Cooke's (much) later years, the trend is reversed and f0 begins to rise, then so does F1: The falling (age 40-81) then rising (age 82-94) trend in F1 is not likely to be explicable by vocal tract lengthening then shortening.

  17. So we probably instead need to look for physiological or auditory mechanisms that affect f0 and F1 in equal measure with increasing age.

  18. Auditory explanation The difference f0 (Bark) – F1 (Bark) has been shown in various studies by Traunmüller to be related to phonetic vowel height. Perhaps speakers compensate for a physiologically induced f0-lowering by lowering F1 (so that phonetic vowel height stays roughly the same).

  19. So based on the above findings in 3., perhaps log(f0) and log(F1) decrease almost linearly with increasing age because of 2. Physiological explanation 1. Various studies point to a reduction in the pulmonary function (Ptacek et al, 1966), laryngeal cartilage ossification, an increased stiffening of the vocal folds (Kahane, 1987), and a reduction in vocal fold closure (Ferrand, 2002) with increasing age. 2. This suggests that it may become more difficult to develop the same acoustic power for the same degree of physiological effort with increasing age. 3. Traunmüller and Ericksson (2000) have found that greater vocal effort produces a boost to f0 and F1. Moreoever, when vocal effort increases they found, (just like in this study) that log(f0) covaries almost linearly with log(F1).

  20. Thank you!

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