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.

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.

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)

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)

1.

2.

Motivation: longitudinal study

Verdonck-de Leeuw and Mahieu, 2004, Journal of Voice'Longitudinal studies on vocal aging are scarce..'

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…

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.

Age and f0

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."

scarcely any change in mean f0 with increasing age in men or women. (e.g Benjamin, 1981; Ramig & Ringel, 1983).

But contrary to 2:

f0 lowers in males from middle to old age (DeCoster & Debruyne, 1997)

mean f0 is not a reliable cue for age (Harnsberger et al, 2006)

Contrary to 1:

Formant lowering with increasing age: Linville & Fisher, 1985, Xue & Hao 2003; Watson & Munson, 2007

Age and formants

Laver & Trudgill (1979): the entire respiratory systemand 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…

Physiological interpretation

On the other hand, with increasing age:

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.

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.

Age-related formant changes are vowel specific (Rastatter et al, 1997; Watson & Munson, 2007)

Age and formants

Xue & Hao (2003) report only oral but not pharyngeal tract lengthening and changes predominantly to F1.

Method: Speakers Two speakers: data from several years over roughly a 50 year period

Four speakers data from two years 30-40 years apart.

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).

Method

We report results on mean f0 and mean F1-F3 (a) in schwa vowels (b) across all periodically voiced frames

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').

Since we obtained a very similar pattern of results from (a) and (b), we present only the results from (b) here.

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.

f0 is significantly lower in later broadcasts

F1 is significantly lower in later broadcasts.

05

01

00

20

0

01

00

30

05

00

early

late

(Speakers from L to R: Cooke, Plomley, Bradman, Hillary, Lockwood, Queen)

C P B H L Q C P B H L Q

mean f0 mean F1

Fre

que

ncy

(Hz)

Results II: F2 and F3

No consistent or significant effect across the 6 speakers on average F2 nor average F3 from early to later broadcasts

early

late

C P B H L Q C P B H L Q1.2

1.4

1.6

1.8

Fre

que

ncy

(kH

z) F3F2

2.2

2.4

2.6

2.8

(Speakers from L to R: Cooke, Plomley, Bradman, Hillary, Lockwood, Queen)

Mean F2 and F3 from early (in the 1940s/1950s vs. late (1980s/1990s) broadcasts in all 6 speakers.

Queen

Cooke

Results III: f0 and F1 averaged separately by year over a 50 year period in the Queen and Alistair Cooke

200

240

280

200

240

280

50 60 70 80 9050 60 70 80 90 00

Hz

400

450

500

550

400

450

500

550

50 60 70 80 9050 60 70 80 90 00

Hz

Fre

quen

cy10

011

012

013

010

011

012

013

0

Hz

Fre

quen

cy

50 60 70 80 9070 80 90 0032

036

040

032

036

040

0

Hz

50 60 70 80 9070 80 90 00

Decade

f0 F1

We found that these data could be modelled with an exponential of the form

yearkrF (separately for F = f0 and F = F1)

R2: 0.7768

R2: 0.723R2 = 0.7722

R2 = 0.6723

f0 rises again in very old age

yearkrf 0

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.

yearkrF 1

)log()log()0log( kyearrf )log()log()1log( kyearrF

50 60 70 80 90 00

5.4

5.6

5.8

6.0

50 60 70 80

5.0

5.5

6.0

F1

f0

QueenCooke

Decade

Log

freq

uenc

y

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.

Do f0 and F1 decrease at a similar rate?

Therefore f0 and F1 decay exponentially in time with increasing age at about the same rate.

Queen

Cooke

Results IV: F2 and F3 averaged separately by year over a 50 year period in the Queen and Alistair Cooke

50 70 90 50 70 90

1.7

1.8

2.8

2.9

50 60 70 80 90 50 60 70 80 90

1.46

1.50

2.50

2.60

2.55

F2 F3

Decade

No significant linear or exponential trend in F2 or F3 as a function of year for either the Queen or Cooke.

Fre

que

ncy

(kH

z)

Summary of results

% decrease in f0

Cooke 42-8212 26

Plomley 37-71 7 23

Bradman 40-7925 21

Hillary 36-7318 16

Lockwood 35-6425 17Queen 27-69

20 19

% decrease in F1Between theage of:

(a) across two years

(b) approx. every other year over a 50 year period in two speakers (Cooke, Queen)

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

No consistent effects in F2 nor F3 in either (a) or (b)

Interpretations: age and vocal/oral tract lengtheningIt 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.

4.60 4.65 4.70 4.75

5.65

5.70

5.75

5.80

82

83

84 85

8688 89

90

91

9293

94

log

F1

log f0

log f0 x log F1 for Cooke between the age of 82 and 94 years

R2 = 0.52, p < 0.001)

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

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).

Physiological explanation1. 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).

So based on the above findings in 3., perhaps log(f0) and log(F1) decrease almost linearly with increasing age because of 2.

Thank you!