M9.1: Ambiguous Patterns of Relative Spectral Energy Maxima and  Ambiguous Formant Patterns

Content of illustration

Figures 1 to 21 show series of sounds of different vowels produced at different F0 but exhibiting similar patterns of relative spectral energy maxima and/or similar patterns of calculated formant frequencies within their supposed vowel-specific frequency range related to statistical F1 and F2. In all cases, the actual differences of the patterns for the sounds of different vowels presented in a single series are far smaller than the observable differences (variations) of corresponding patterns for sounds of a single vowel.—In some series that include sounds at high fundamental frequencies, the overall spectral envelopes and the harmonic spectra are considered for the comparison in question.

For each series, roughly estimated average frequencies of the two lower relative spectral energy maxima and/or of the calculated frequencies F1–F2 are given below in terms of model patterns for the sounds compared. Exceptions concern a few comparisons of sounds of back vowels, for which only a single spectral peak is manifest in the sound spectra (for these comparisons, the corresponding peak frequency is given), and an additional exception concerns a comparison of sounds /a–ɑ, u /, for which only the spectrum as such > 1.5 kHz is considered.

The first sound series shown include sounds of the vowels /a–ɑ, o, u /, divided into two groups, one presenting sounds of different speakers, the other presenting sounds of single speakers. The second series shown include sounds of front vowels, again divided into the two groups mentioned. (Figures 9 and 11 include exceptions that illustrate the ambiguity discussed for sounds of different and of single speakers.) Within a series, the sounds are organised according to fundamental frequency.

Comparisons of sounds of back vowels and of /a–ɑ / produced by different speakers: 

• Figure 1 shows sounds of /a–ɑ, o, u /; model pattern of spectral peaks and/or of calculated formant frequencies = 600–1200 Hz
• Figure 2 shows sounds of /a–ɑ, o, u /; model pattern of spectral peaks and/or of calculated formant frequencies = 600–1050 Hz
• Figure 3 shows sounds of /a–ɑ, o /; model pattern of spectral peaks and/ or of calculated formant frequencies = 660–1320 Hz
  

Sounds of /u / are included in the first three series because the first harmonic corresponds to F1 of the model pattern in question; however, no clear spectral indication can be found for F2 even if LPC analysis gives a (weak) second formant at a frequency level which corresponds to the model pattern of a series.

Comparisons of sounds of back vowels and of /a–ɑ / produced by single speakers:

• Figure 4 shows three comparisons of sounds of /a–ɑ, o, u / produced by a man and two women; model pattern of spectral peaks and/or of calculated formant frequencies = 600–1200 Hz
  
• Figure 5 shows two comparisons of sounds of /a–ɑ, o / produced by a man (sounds sung by a tenor); model pattern of spectral peaks and/or of calculated formant frequencies = 600– 1200 Hz for the first comparison, similar spectral peaks and spectral envelopes for the second comparison
  
• Figure 6 shows sounds of /a–ɑ / and of /u / produced by a woman which exhibit comparable spectral envelopes < 1.5 kHz
  
• Figure 7 shows sounds of /ɔ, o, u / produced by a woman; model pattern of spectral peaks and/or of calculated formant frequencies = one clear peak at c. 550 Hz (exceptionally, sounds of the vowel /ɔ / are included in order to show a possible shift in perceived vowel quality from /ɔ / to /o / related to two levels of F0 of c. 175 Hz and c. 260 Hz)
  
• Figure 8 shows two comparisons of sounds of /o, u / produced by two children (age 12 and 6); model patterns of spectral peaks and/or of calculated formant frequencies = one clear peak at c. 400 Hz (first sound pair) and at c. 520 Hz (second sound pair), respectively.
  

Comparisons of sounds of front vowels produced by different speakers: In contrast to many other comparisons presented in this chapter, the ambiguity illustrated in Figures 9 to 11 does not always relate to substantial differences in F0 but also to the configuration of the levels of the harmonics, to the spectrum above F2 and to the levels of calculated formants including F3. This is the case particularly for direct comparisons of sounds of /e / and of /ø /, and of / i / and of /y/, respectively. Moreover, a sound produced with creak phonation is exceptionally included into the comparison (see the first vowel spectrum of Figure 9).—Comparisons:

• Figure 9 shows sounds of /ø, e, y, i /; model pattern of spectral peaks and/or of calculated formant frequencies = 330–2000 Hz; note the ambiguity for sounds of /ø, i / for the single speaker 391 and the ambiguity for the sounds of /ø, y/ for the single speaker 376
  
• Figure 10 shows sounds of /ø, e, y, i /; model pattern of spectral peaks and/or of calculated formant frequencies = 350–2150 Hz
  
• Figure 11 shows sounds of /ø, e, y, i /; model pattern of spectral peaks and/ or of calculated formant frequencies = 420–2150 Hz; note the ambiguity for sounds of /ø, y/ for the single speaker 402
  
• Figure 12 shows sounds of /ɛ, e, i /; model pattern of spectral peaks and/ or of calculated formant frequencies = 500–2250 Hz
  
• Figure 13 shows sounds of /ɛ, e, i /; model pattern of spectral peaks and/ or of calculated formant frequencies = 600–2450 Hz
  
• Figure 14 shows sounds of /e, i /; model pattern of spectral peaks and/ or of calculated formant frequencies = 400–2600 Hz
  
• Figure 15 shows sounds of /ɛ, e, y/; model pattern of spectral peaks and/ or of calculated formant frequencies = 500–2000 Hz
  
• Figure 16 shows sounds of /ɛ, ø, y/; model pattern of spectral peaks and/ or of calculated formant frequencies = 430–2000 Hz
  
• Figure 17 shows sounds of /ɛ, ø, y/; model pattern of spectral peaks and/ or of calculated formant frequencies = 475–1900 Hz
  
• Figure 18 shows sounds of /ɛ, y/; model pattern of spectral peaks and/ or of calculated formant frequencies = 650–1950 Hz
  

Comparisons of sounds of front vowels, produced by single speakers: 

• Figure 19 shows two comparisons of sounds of /ɛ, e, i / produced by two women; model patterns of spectral peaks and/or of calculated formant frequencies = 510–2550 Hz and 600–2400 Hz, respectively
  
• Figure 20 shows three comparisons of sounds of /e, i / produced by three children (age 7 to 9); model patterns of spectral peaks and/ or of calculated formant frequencies = 450–3000 Hz and 400–3000 Hz, respectively
  
• Figure 21 shows three comparisons of sounds of /ø, y/ produced by a man, a woman and a child (age 12); model patterns of spectral peaks and/or of calculated formant frequencies = 320– 1600 Hz, 320–2000 Hz and 400–2000 Hz, respectively
  

For earlier accounts, see Maurer and Landis (2000).

Comparisons of /a–ɑ, o, u/ produced by different speakers – links to the spectra of the figures

Figure 1: Sounds of /a–ɑ, o, u/; related model pattern = 600–1200 Hz.

>> Link to Figure 1

Figure 2: Sounds of /a–ɑ, o, u/; related model pattern = 600–1050 Hz.

>> Link to Figure 2

Figure 3: Sounds of /a–ɑ, o, u/: related model pattern = 660–1320 Hz.

>> Link to Figure 3

Comparisons of sounds of back vowels and of /a–ɑ/, produced by single speakers – links to the spectra of the figures

Figure 4: Three comparisons of sounds of /a–ɑ, o, u/ produced by a man and two women; related model pattern = 600–1200 Hz.

>> Link to Figure 4

Figure 5: Two comparisons of sounds of /a–ɑ, o/ produced by a man (sounds sung by a tenor); related model pattern = 600–1200 Hz for the first comparison; similar spectral peak and spectral envelopes for the second comparison.

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Figure 6: Sounds of /a–ɑ/ and /u/, produced by a woman, which exhibit comparable spectral envelopes < 1.5 kHz.

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Figure 7: Sounds of  /ɔ, o, u/, produced by a woman; related model pattern = one clear peak at c. 550 Hz.

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Figure 8: Two comparisons of sounds of /o, u/ produced by two children (age 12 and 6); related model patterns = one clear peak at c. 400 Hz (first sound pair) and at c. 520 Hz (second sound pair), respectively.

>> Link to Figure 8

Comparisons of sounds of front vowels, produced by different speakers – links to the spectra of the figures

Figure 9. Sounds of /ø, e, y, i/; related model pattern = 330–2000 Hz.

>> Link to Figure 9

Figure 10. Sounds of /ø, e, y, i/; related model pattern = 350–2150 Hz.

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Figure 11. Sounds of /ø, e, y, i/; related model pattern = 420–2150 Hz.

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Figure 12: Sounds of /ɛ, e i/; relatedmodel pattern = 500–2250 Hz.

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Figure 13: Sounds of /ɛ, e, i/; related model pattern = 600–2450 Hz.

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Figure 14: Sounds of /e, i/; related model pattern = 400–2600 Hz.

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Figure 15: Sounds of /ɛ, e, y/; related model pattern = 500–2000 Hz.

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Figure 16:  Sounds of /ɛ, ø, y/; related model pattern = 430–2000 Hz.

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Figure 17: Sounds of /ɛ, ø, y/; related model pattern = 475–1900 Hz.

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Figure 18: Sounds of /ɛ, y/; related model = 650–1950 Hz.

>> Link to Figure 18

Comparisons of sounds of front vowels, produced by single speakers – links to the spectra of the figures

Figure 19: Two comparisons of sounds of /ɛ, e, i/ produced by two women; related model patterns = 510–2550 Hz and 600–2400 Hz, respectively.

>> Link to Figure 19

Figure 20: Three comparisons of sounds of /e, i/ produced by three children; related model patterns = 450–3000 Hz and 400–3000 Hz, respectively.

>> Link to Figure 20

Figure 21: Three comparisons of sounds of /ø, y/ produced by a man, a woman and a child (age 12); related model patterns = 320–1600 Hz, 320–2000 Hz and 400–2000 Hz, respectively.

>> Link to Figure 21