Static measurements of vowel formant frequencies and bandwidths: A review

Abstract

Purpose: Data on vowel formants have been derived primarily from static measures representing an assumed steady state. This review summarizes data on formant frequencies and bandwidths for American English and also addresses (a) sources of variability (focusing on speech sample and time sampling point), and (b) methods of data reduction such as vowel area and dispersion.

Method: Searches were conducted with CINAHL, Google Scholar, MEDLINE/PubMed, SCOPUS, and other online sources including legacy articles and references. The primary search items were vowels, vowel space area, vowel dispersion, formants, formant frequency, and formant bandwidth.

Results: Data on formant frequencies and bandwidths are available for both sexes over the lifespan, but considerable variability in results across studies affects even features of the basic vowel quadrilateral. Origins of variability likely include differences in speech sample and time sampling point. The data reveal the emergence of sex differences by 4 years of age, maturational reductions in formant bandwidth, and decreased formant frequencies with advancing age in some persons. It appears that a combination of methods of data reduction provide for optimal data interpretation.

Conclusion: The lifespan database on vowel formants shows considerable variability within specific age-sex groups, pointing to the need for standardized procedures.

Figure 1

Upper part: spectrogram with LPC formant tracks for vowel /ae/ produced by a young woman, illustrating a diphthongal formant pattern and vocal fry at the end of the vocalic segment. Lower part: Spectrogram with LPC formant tracks for vowel /u/, produced by a young man, illustrating continuous decline in F2 frequency over the duration of the vowel. In both spectrograms, formants are labeled F1 to F4 and frequency in kHz is shown at the left margin. The vertical lines indicate three potential time points of formant measurement: (a) near vowel onset, (b) midpoint, and (c) near vowel end. The double-headed arrows indicate F2-F1 separation at different time points. Spectrograms are from analyses done with the software TF32 (Milenkovic, 2010), with unsmoothed LPC formant tracks.

Figure 2

Frequency ranges for F1, F2, F3, and F4 (as available) for men, women, and children. Data sources are as follows: men, women, and children ages 10-12 (Hillenbrand et al., 1995); girls age 5 (S. Lee et al., 1997); Children age 3 and Children age 2 (McGowan et al., 2014).

Figure 3

a. F1-F2 plots for men showing values for the point vowels reported in the 7 studies listed in Table 1. The thick line is the vowel quadrilateral from Peterson and Barney (1952). b. F1-F2 plots for women showing values for the point vowels reported in the 7 studies listed in Table 1. The thick line is the vowel quadrilateral from Peterson and Barney (1952).

Figure 3

a. F1-F2 plots for men showing values for the point vowels reported in the 7 studies listed in Table 1. The thick line is the vowel quadrilateral from Peterson and Barney (1952). b. F1-F2 plots for women showing values for the point vowels reported in the 7 studies listed in Table 1. The thick line is the vowel quadrilateral from Peterson and Barney (1952).

Figure 4

a. Vowel quadrilaterals for men derived from the data in 4 studies: (a) Hillenbrand et al., (1995), (b) Zahorian and Jagharghi (1993) (c) Peterson and Barney (1952), and (d) Childers and Wu (1991). Intersecting diagonals have been drawn from the corner points. b. Vowel quadrilaterals for women derived from the data in 4 studies: (a) Hillenbrand et al., (1995), (b) Zahorian and Jagharghi (1993) (c) Peterson and Barney (1952), and (d) Childers and Wu (1991). Intersecting diagonals have been drawn from the corner points.

Figure 4

a. Vowel quadrilaterals for men derived from the data in 4 studies: (a) Hillenbrand et al., (1995), (b) Zahorian and Jagharghi (1993) (c) Peterson and Barney (1952), and (d) Childers and Wu (1991). Intersecting diagonals have been drawn from the corner points. b. Vowel quadrilaterals for women derived from the data in 4 studies: (a) Hillenbrand et al., (1995), (b) Zahorian and Jagharghi (1993) (c) Peterson and Barney (1952), and (d) Childers and Wu (1991). Intersecting diagonals have been drawn from the corner points.