PHREND at UCSC Sepember 24, 2016 Sarah Bakst, UC Berkeley Modeling the effect of palate shape on the articulation and acoustics of American English /r/ PHREND at UCSC Sepember 24, 2016 Sarah Bakst, UC Berkeley

Overview What is the role of individual anatomy in speech production? Here: domedness of palate Mapping between articulation and acoustics Test case: American English /r/ This work models an answer to the question, “what is the role of individual anatomy in speech production?”

Role of palate shape Brunner et al. (2009): flatness correlated with reduced articulatory variability but not acoustic variability for front vowels Bakst (2016): extension to /r/

Articulatory variability Articulatory and acoustic variability compared by palate shape in /r/ production Articulatory variability (z-scored) pdf(‘rtic.pdf’, height = 6, width = 10) plot(dd$rscale~dd$alpha, main = 'Variability in production correlated with palate shape for /r/ ', ylim = c(-2,2), xlab = 'Flatness', ylab = 'Variability', type = 'n') points(dd$rscale~dd$alpha, pch = 15) abline(3.552,-1.728) dev.off() plot(dd$f3scale~dd$alpha, col = 'red') abline(1.4910,-0.7256, col = 'red', lty = 2) Acoustic variability (z-scored F3 s.d.) 1.8 2.0 2.2 2.4 2.6 Palate flatness

Quantal mapping arbitrary constriction along vocal tract (figure from Stevens & Keyser 2010)

Domedness as a factor Palate shape affects mapping between articulation and acoustics (Stevens 1972) Differences in width of zone II Differences in location and frequency of discontinuities

Motivation Observation: flat palates -> reduced articulatory variability What is the nature of this relationship between palate shape and articulatory/acoustic variability? Is the articulatory-acoustic mapping actually different for different palate shapes? Or is there just less room to move? Test with F3 in /r/ as acoustic parameter

Hypothesis Main hypothesis: Less linear mapping = Wider ‘zone II’ for flatter palates, hence constrained articulatory variability Less linear mapping = larger areas of local acoustic stability (domed) more discontinuities in F3 values for domed palates More linear mapping = more acoustic flexibility (flat) Greater range in F3 value for flatter palates

Modeling in Maeda Maeda synthesizer Default: one relatively domed-average palate four articulatory principal components based on real human: jaw/tube dorsum position dorsum shape apex position

Maeda revised New parameter: apex orientation ant post ant bunched /r/ retroflex /r/ bunched /r/

Tongue tip lips glottis

Palates Maeda comes with one default palate I additionally created a flat palate and a super-domed palate

New palates

Methods Settings for each parameter (below: dorsum shape) on a scale from -4 to 4 Component multiplied by setting

Method Four manipulated parameters: Dorsum position (anteriority) Dorsum shape (bunchiness) Apex shape (tip-up/-down) Lip protrusion Python script looped over values for each articulatory parameter Model plays through vocal tract Formant tracking in ifc formant Rejection of bad tokens: low rms amplitude

Area function Area taken at 32 places along vocal tract Synthesizer uses special formula taking into account domedness of palate: A (x) = αx^β α is a metric of domedness; x = width in sagittal plane α empirically-derived

Results: Zone width

Correlations with F3 Flat Default Domed Dorsum position -0.52 -0.64 -0.63 Dorsum shape -0.47 -0.32 -0.19 Lip protrusion -0.05 -0.14 -0.24 Tip curl -0.09

Correlations with F3 Flat Default Domed Dorsum position -0.52 -0.64 -0.63 Dorsum shape -0.47 -0.32 -0.19 Lip protrusion -0.05 -0.14 -0.24 Tip curl -0.09

Correlations with F3 Flat Default Domed Dorsum position -0.52 -0.64 -0.63 Dorsum shape -0.47 -0.32 -0.19 Lip protrusion -0.05 -0.14 -0.24 Tip curl -0.09

Correlations with F3 Flat Default Domed Dorsum position -0.52 -0.64 -0.63 Dorsum shape -0.47 -0.32 -0.19 Lip protrusion -0.05 -0.14 -0.24 Tip curl -0.09

Correlations with F3 Flat Default Domed Dorsum position -0.52 -0.64 -0.63 Dorsum shape -0.47 -0.32 -0.19 Lip protrusion -0.05 -0.14 -0.24 Tip curl -0.09

Lowest F3 configurations

Discussion Smallest “zone I” for flattest palate–theoretically a wider range of attainable acoustic output Effect of each articulator on F3 actually varies by palate shape Supports result linking reduced articulatory variability with flatter palate shape

Conclusions Palate shape does seem to have an influence over the articulatory-acoustic mapping Implications for sound change? Next step: add sublingual cavity expectations: sublingual cavity significant lowering effect (usually on F3) better articulatory predictions

Acknowledgements Ronald Sprouse Keith Johnson Susan Lin John Houde Rich Ivry Members of the UC Berkeley Phon Lab

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