1. Laryngeal correlates of the English tense/lax vowel contrast
Olga Gordeeva
13 December, 2005
CNTS
University of Antwerp

2. Question and Background
Systemic differences involving tense/lax vowel contrast are part of my PhD: on the acquisition of vowel quality, duration, vocal effort by Russian/SSE bilingual pre-schoolers.
One of the conclusions: tense/lax vowel contrast is more difficult to acquire than the realisational differences such as between /¬ u/ (Panasyuk et al., 1995; Markus & Bond, 1999; Escudero, 2000; Guion, 2003; Piske et al., 2002)
Does the English tense/lax vowel contrast involve only differences vowel quality and length, or do they vary along other phonetic dimensions?
This presentation: based on the results from my English-speaking adult controls, a partly on my postdoctoral work involving EGG.

3. Introduction (2) [i] [I]
The CHEAP/CHIP vowel contrast is often described in terms more extreme values for the tense vowels due to higher muscular tension and more extreme movements of the articulators, longer duration (discussion in Trask, 1996).
Stevens (1998, p.297) hypothesised laryngeal involvement on top of segmental differences: a more breathy phonation for tense vowels, and a less breathy one for the lax vowels resulting from the greater vocal tract constriction for the high vowels.
Acoustic consequence of this laryngeal adjustment  lax vowels have enhanced intensity in midfrequencies compared to the tense ones
Jessen (2002) provided supportive evidence for Steven’s statement for German tense/lax contrast on both acoustic and laryngeal EGG level.

4. Adopted from Gauffin & Sundberg (1989) study
Introduction (3)
Glottal pulse
Radiated Spectrum
Transglottal airflow
(arbitrary units)
Time (arbitrary units)
Sound Pressure Level
Frequency
Adopted from Gauffin & Sundberg (1989) study

5. This presentation
Review the acoustic evidence of spectral tilt differences between SSE/SBE tense/lax close(-mid) vowels /i I/ and /u U/
Try to link the acoustic results for SBE to the more direct EGG analysis of the glottal pulse
Introduce the EGG method used
Present preliminary EGG results based on the MOCHA corpus

6. Acoustic evidence Gordeeva (2005) (1)
5 SSE adults and 4 SBE adults (all female)
Materials 12 CVC words with the /i I/ and /u U/
Embedded in utterances in four prosodic positions
E.g. “It’s a sheep” “A sheep is a sheep, and nothing but a sheep.”
Spectral tilt was measured as an RMS-power (dB) difference of F1 and F2 in fixed bands (Sluijter, 1995; Sluijter et al. 1996)
Data was normalised for differences in formant structure following Hanson (1997) and Jessen (2002)
Statistical analysis: mixed design ANOVA with fixed factors “Language” (SSE or SSBE), “Vowel” (tense or lax), and normalised SPL level in F2 as a dependent variable

7. Acoustic evidence Gordeeva (2005) (2)
If /i/ has a more spectral tilt than /I/ in both SSE and SBE

8. Gordeeva (2005) SBE /u U/ and SSE short and long /¬/ (3)

9. Summary acoustic results
Our acoustic data for SSE/SBE supports Jessen’s (2002) acoustic results for German, and Steven’s (1998) suggestion.
In SSE/SBE, more spectral tilt is associated with the tense high vowels than with the lax ones. There is more acoustic energy loss in the vocal tract for the tense vowels.
Gradual difference? speakers spend more laryngeal effort to produce the lax vowels (adopting a less breathy phonation for the lax vowels)
Categorical voice quality difference? The steepness of the spectral tilt may also serve as an indicator of the presence of creaky voice (Laver, 1980; Klatt & Klatt, 1990)

10. Current EGG study
Confirm the acoustic results for SSE / SBE based on more direct EGG evidence
SBE pilot based on the MOCHA corpus
2 SBE speakers: 1 female and 1 male
EGG data, phonetic labelling, and acoustic waveform
Tokens of /i/ versus /I/ and /u/ versus /U/ with vowel duration > 60 ms
All cycles within the vowel boundaries (except for the first and the last one)

11. EGG signal model Marasek (1997)

12. EGG parametrisation
Derived using Marasek’s (1997) model of EGG signal implemented as a Praat script
the EGG signal and phonetic segmentation of duration as input
Outputs relevant cycle-by-cycle parameters:
Closing quotient: duration of the closing phase relative to T
Speed Quotient: skewness of the glottal pulse (duration of the closing phase relative to the opening phase)
Closing Slope: skewness / steepness of the closing phase
Pitch: indication of vowel-intrinsic pitch and subglottal pressure
Peak-to-peak amplitude: indication of subglottal pressure
Plus long-term parameters Jitter (F0 fluctutation) and Shimmer (amplitude fluctuation)
Skewness
parameters

13. EGG signal model Marasek (1997)

14. Results: EGG Cslope

15. Shimmer (amplitude fluctuation)

16. Jitter (F0 fluctuation)

17. Analysis and Results
Multivariate ANOVA with tense/lax vowel and speaker as fixed factors
And OQ, CSlope, CQ, SQ, Jitter, Shimmer and OI as dependent variables
 Effects & Interactions OQ
Cslope CQ SQ
Jitter
Shimmer OI uU **
speaker
uU*speaker iI *
iI*speaker
highly significant
Significant

18. Summary EGG results
There were no systematic differences in between the tense/lax vowels in OQ, CQ, SQ and intensity
As suggested by Marashek (1997), the Cslope parameter might be a better predictor of the skewness in the EGG domain
The lax vowels are produced with a less breathy laryngeal configuration than the tense ones Significant shimmer/jitter differences indicate that there might be a categorical voice quality difference involved (e.g. it is compatible with a more creaky phonation type in the lax vowels)

19. Summary
[i]
[I]

20. Implications
Whether this difference in spectral tilt is a consequence of a gradual or categorical voice quality adjustment: the tense/lax vowel distinction in English seems to involve a triple phonetic distinction: segmental, durational and laryngeal.
In L2 acquisition context: the lax vowel is difficult to acquire.
Studies involving perceptual cues to the contrast may need to look at the laryngeal level as well as segmental.

21. Further Plans Record more controlled EGG materials for SSE
Control utterance position
Consider prominence issues (stressed unaccented versus stressed accented)
Control for segmental context (minimal pairs)
Consider vowel height
Correlate spectral tilt and EGG skewness measures