In speech production, the anatomical morphology forms the substrate on which the speakers build their articulatory strategy to reach specific articulatory-acoustic goals. The aim of this study is to characterize morphological inter-speaker variability by building a shape model of the full vocal tract including hard and soft structures. Static magnetic resonance imaging data from 41 speakers articulating altogether 1947 phonemes were considered, and the midsagittal articulator contours were manually outlined. A phoneme-independent average-articulation representative of morphology was calculated as the speaker mean articulation. A principal component analysis-driven shape model was derived from average-articulations, leading to five morphological components, which explained 87% of the variance. Almost three-quarters of the variance was related to independent variations of the horizontal oral and vertical pharyngeal lengths, the latter capturing male-female differences. The three additional components captured shape variations related to head tilt and palate shape. Plane wave propagation acoustic simulations were run to characterize morphological components. A lengthening of 1 cm of the vocal tract in the vertical or horizontal directions led to a decrease in formant values of 7%–8%. Further analyses are required to analyze three-dimensional variability and to understand the morphological-acoustic relationships per phoneme. Average-articulations and model code are publicly available (https://github.com/tonioser/VTMorphologicalModel).

1.
Apostol
,
L.
,
Perrier
,
P.
, and
Bailly
,
G.
(
2004
). “
A model of acoustic interspeaker variability based on the concept of formant-cavity affiliation
,”
J. Acoust. Soc. Am.
115
,
337
351
.
2.
Arens
,
R.
,
McDonough
,
J. M.
,
Corbin
,
A. M.
,
Hernandez
,
M. E.
,
Maislin
,
G.
,
Schwab
,
R. J.
, and
Pack
,
A. I.
(
2002
). “
Linear dimensions of the upper airway structure during development
,”
Am. J. Respir. Crit. Care Med.
165
,
117
122
.
3.
Badin
,
P.
,
Bailly
,
G.
,
Revéret
,
L.
,
Baciu
,
M.
,
Segebarth
,
C.
, and
Savariaux
,
C.
(
2002
). “
Three-dimensional linear articulatory modeling of tongue, lips and face, based on MRI and video images
,”
J. Phon.
30
,
533
553
.
4.
Badin
,
P.
, and
Fant
,
G.
(
1984
). “
Notes on vocal tract computation
,”
Speech Transm. Lab. Q. Prog. Status Rep.
25
,
53
108
.
5.
Badin
,
P.
,
Perrier
,
P.
,
Boe
,
L.-J.
, and
Abry
,
C.
(
1990
). “
Vocalic nomograms: Acoustic and articulatory considerations upon formant convergences
,”
J. Acoust. Soc. Am.
87
,
1290
1300
.
6.
Badin
,
P.
,
Sawallis
,
T. R.
,
Crépel
,
S.
, and
Lamalle
,
L.
(
2014
). “
Comparison of articulatory strategies for a bilingual speaker: Preliminary data and models
,” in
Proceedings of the 10th International Seminar on Speech Production (ISSP10)
, May 5–8, Cologne, Germany.
7.
Bakst
,
S.
(
2021
). “
Palate shape influence depends on the segment: Articulatory and acoustic variability in American English /ɹ/ and /s/
,”
J. Acoust. Soc. Am.
149
,
960
971
.
8.
Bakst
,
S.
, and
Johnson
,
K.
(
2018
). “
Modeling the effect of palate shape on the articulatory-acoustics mapping
,”
J. Acoust. Soc. Am.
144
,
EL71
EL75
.
9.
Bakst
,
S.
, and
Lin
,
S.
(
2015
). “
An ultrasound investigation into articulatory variation in American /r/ and /s/
,” in
Proceedings of the 18th International Congress of Phonetic Sciences (ICPhS)
, August 10–14, Glasgow, UK.
10.
Barbier
,
G.
,
Boë
,
L.-J.
,
Captier
,
G.
, and
Laboissière
,
R.
(
2015
). “
Human vocal tract growth: A longitudinal study of the development of various anatomical structures
,” in
Proceedings of Interspeech 2015
, September 6–10, Dresden, Germany.
11.
Baum
,
S. R.
, and
McFarland
,
D. H.
(
1997
). “
The development of speech adaptation to an artificial palate
,”
J. Acoust. Soc. Am.
102
,
2353
2359
.
12.
Beautemps
,
D.
,
Badin
,
P.
, and
Bailly
,
G.
(
2001
). “
Linear degrees of freedom in speech production: Analysis of cineradio- and labio-film data and articulatory-acoustic modeling
,”
J. Acoust. Soc. Am.
109
,
2165
2180
.
13.
Birkholz
,
P.
,
Kürbis
,
S.
,
Stone
,
S.
,
Häsner
,
P.
,
Blandin
,
R.
, and
Fleischer
,
M.
(
2020
). “
Printable 3D vocal tract shapes from MRI data and their acoustic and aerodynamic properties
,”
Sci. Data
7
,
255
.
14.
Brunner
,
J.
,
Fuchs
,
S.
, and
Perrier
,
P.
(
2005
). “
The influence of the palate shape on articulatory token-to-token variability
,”
ZAS Pap. Linguist.
42
,
43
67
.
15.
Brunner
,
J.
,
Fuchs
,
S.
, and
Perrier
,
P.
(
2009
). “
On the relationship between palate shape and articulatory behavior
,”
J. Acoust. Soc. Am.
125
,
3936
3949
.
16.
Brunner
,
J.
,
Hoole
,
P.
, and
Perrier
,
P.
(
2007
). “
Articulatory optimisation in perturbed vowel articulation
,” in
Proceedings of the 16th International Congress of Phonetic Sciences (ICPhS)
, August 6–10, Saarbrücken, Germany, pp.
497
500
.
17.
Cai
,
J.
,
Laprie
,
Y.
,
Busset
,
J.
, and
Hirsch
,
F.
(
2009
). “
Articulatory modeling based on semi-polar coordinates and guided PCA technique
,” in
Proceedings of Interspeech 2009
, September 6–10, Brighton, UK, pp.
56
59
.
18.
Chiba
,
T.
, and
Kajiyama
,
M.
(
1941
).
The Vowel: Its Nature and Structure
(
Tokyo-Kaiseikan
,
Tokyo, Japan
).
19.
Chiu
,
C.
,
Weng
,
Y.
, and
Chen
,
B.
(
2022
). “
Tongue postures and tongue centers: A study of acoustic-articulatory correspondences across different head angles
,”
Front. Psychol.
12
,
768754
.
20.
Chovalopoulou
,
M.-E.
,
Valakos
,
E. D.
, and
Manolis
,
S. K.
(
2013
). “
Sex determination by three-dimensional geometric morphometrics of the palate and cranial base
,”
Anthropol. Anz.
70
,
407
425
.
21.
Chuang
,
Y. J.
,
Hwang
,
S. J.
,
Buhr
,
K. A.
,
Miller
,
C. A.
,
Avey
,
G. D.
,
Story
,
B. H.
, and
Vorperian
,
H. K.
(
2022
). “
Anatomic development of the upper airway during the first five years of life: A three-dimensional imaging study
,”
PLoS One
17
,
e0264981
.
22.
Dediu
,
D.
,
Janssen
,
R.
, and
Moisik
,
S. R.
(
2019
). “
Weak biases emerging from vocal tract anatomy shape the repeated transmission of vowels
,”
Nat. Hum. Behav.
3
,
1107
1115
.
23.
Dediu
,
D.
, and
Moisik
,
S. R.
(
2019
). “
Pushes and pulls from below: Anatomical variation, articulation and sound change
,”
Glossa
4
(
1
),
7
.
24.
Evereklioglu
,
C.
,
Doganay
,
S.
,
Er
,
H.
,
Gunduz
,
A.
,
Tercan
,
M.
,
Balat
,
A.
, and
Cumurcu
,
T.
(
2002
). “
Craniofacial anthropometry in a Turkish population
,”
Cleft Palate Craniofac. J.
39
,
208
218
.
25.
Fant
,
G.
(
1960
).
Acoustic Theory of Speech Production
(
Mouton
,
The Hague, Netherlands
).
26.
Fant
,
G.
(
1966
). “
A note on vocal tract size factors and non-uniform F-pattern scalings
,”
Speech Transm. Lab. Q. Prog. Status Rep.
7
(
4
),
22
30
.
27.
Fitch
,
W. T.
, and
Giedd
,
J.
(
1999
). “
Morphology and development of the human vocal tract: A study using magnetic resonance imaging
,”
J. Acoust. Soc. Am.
106
,
1511
1522
.
28.
Flanagan
,
J. L.
(
1972
).
Speech Analysis Synthesis and Perception
(
Springer-Verlag
,
Berlin
).
29.
Fuchs
,
S.
,
Perrier
,
P.
,
Geng
,
C.
, and
Mooshammer
,
C.
(
2006
). “
What role does the palate play in speech motor control? Insights from tongue kinematics for German alveolar obstruents
,” in
Speech Production: Models, Phonetic Processes, and Techniques
, edited by
J.
Harrington
and
M.
Tabain
(
Psychology
,
New York
), pp.
149
164
.
30.
Fuchs
,
S.
,
Winkler
,
R.
, and
Perrier
,
P.
(
2008
). “
Do speakers' vocal tract geometries shape their articulatory vowel space?
” in
Proceedings of the 8th International Seminar on Speech Production (ISSP)
, December 8–12, Strasbourg, France, pp.
333
336
.
31.
Goldstein
,
U. G.
(
1980
). “
An articulatory model for the vocal tracts of growing children
,” Ph.D. thesis,
Massachusetts Institute of Technology
,
Cambridge, MA
.
32.
Gross
,
A. M.
,
Kellum
,
G. D.
,
Franz
,
D.
,
Michas
,
K.
,
Walker
,
M.
,
Foster
,
M.
, and
Bishop
,
F. W.
(
1994
). “
A longitudinal evaluation of open mouth posture and maxillary arch width in children
,”
Angle Orthod.
64
,
419
424
.
33.
Hashi
,
M.
,
Westbury
,
J. R.
, and
Honda
,
K.
(
1998
). “
Vowel posture normalization
,”
J. Acoust. Soc. Am.
104
,
2426
2437
.
34.
Hiki
,
S.
, and
Itoh
,
H.
(
1986
). “
Influence of palate shape on lingual articulation
,”
Speech Commun.
5
,
141
158
.
35.
Holbrook
,
R. T.
, and
Carmody
,
F. J.
(
1937
).
X-ray Studies of Speech Articulations: Notes and X-ray Films of the Late Richard T. Holbrook
(
University of California
,
Berkeley, CA
).
36.
Honda
,
K.
,
Maeda
,
S.
,
Hashi
,
M.
,
Dembowski
,
J.
, and
Westbury
,
J. R.
(
1996
). “
Human palate and related structures: Their articulatory consequences
,” in
Proceedings of the 4th International Conference on Spoken Language Processing
, October 3–6, Philadelphia, PA.
37.
Honda
,
M.
,
Fujino
,
A.
, and
Kaburagi
,
T.
(
2002
). “
Compensatory responses of articulators to unexpected perturbation of the palate shape
,”
J. Phon.
30
,
281
302
.
38.
Jan
,
M. A.
,
Marshall
,
I.
, and
Douglas
,
N. J.
(
1994
). “
Effect of posture on upper airway dimensions in normal human
,”
Am. J. Respir. Crit. Care Med.
149
,
145
148
.
39.
Janssen
,
R.
,
Moisik
,
S. R.
, and
Dediu
,
D.
(
2018
). “
Modelling human hard palate shape with Bézier curves
,”
PLoS One
13
,
e0191557
.
40.
Johnson
,
K.
,
Ladefoged
,
P.
, and
Lindau
,
M.
(
1993
). “
Individual differences in vowel production
,”
J. Acoust. Soc. Am.
94
,
701
714
.
41.
King
,
E. W.
(
1952
). “
A roentgenographic study of pharyngeal growth
,”
Angle Orthod.
22
,
23
37
.
42.
Kitamura
,
T.
,
Takemoto
,
H.
,
Honda
,
K.
,
Shimada
,
Y.
,
Fujimoto
,
I.
,
Syakudo
,
Y.
,
Masaki
,
S.
,
Kuroda
,
K.
,
Oku-uchi
,
N.
, and
Senda
,
M.
(
2005
). “
Difference in vocal tract shape between upright and supine postures: Observation by an open-type MRI scanner
,”
Acoust. Sci. Technol.
5
,
465
468
.
43.
Kröger
,
B. J.
(
2022
). “
Computer-implemented articulatory models for speech production: A review
,”
Front. Rob. AI
9
,
796739
.
44.
Ladefoged
,
P.
, and
Broadbent
,
D. E.
(
1957
). “
Information conveyed by vowels
,”
J. Acoust. Soc. Am.
29
,
98
104
.
45.
Ladefoged
,
P.
, and
Johnson
,
K.
(
2011
).
A Course in Phonetics
(
Cengage Learning
,
Boston
).
46.
Lammert
,
A. C.
, and
Narayanan
,
S. S.
(
2015
). “
On short-time estimation of vocal tract length from formant frequencies
,”
PLoS One
10
,
e132193
.
47.
Lammert
,
A.
,
Proctor
,
M.
, and
Narayanan
,
S.
(
2013a
). “
Interspeaker variability in hard palate morphology and vowel production
,”
J. Speech Lang. Hear. Res.
56
,
1924
1933
.
48.
Lammert
,
A.
,
Proctor
,
M.
, and
Narayanan
,
S.
(
2013b
). “
Morphological variation in the adult hard palate and posterior pharyngeal wall
,”
J. Speech Lang. Hear. Res.
56
,
521
530
.
49.
Maeda
,
S.
(
1990
). “
Compensatory articulation during speech: Evidence from the analysis and synthesis of vocal-tract shapes using an articulatory model
,” in
Speech Production and Speech Modelling
, edited by
W. J.
Hardcastle
and
A.
Marchal
(
Kluwer Academic
,
Amsterdam
), pp.
131
149
.
50.
Maeda
,
S.
(
2005
). “
Face models based on a guided PCA of motion-capture data: Speaker dependent variability in /s/-/sh/ contrast production
,”
ZAS Pap. Linguist.
40
,
95
108
.
51.
McCutcheon
,
M. J.
,
Hasegawa
,
A.
, and
Fletcher
,
S. G.
(
1980
). “
Effects of palatal morphology on /s,z/ articulation
,”
J. Acoust. Soc. Am.
67
,
S94
.
52.
Mermelstein
,
P.
(
1973
). “
Articulatory model for the study of speech production
,”
J. Acoust. Soc. Am.
53
,
1070
1082
.
53.
Mooshammer
,
C.
,
Perrier
,
P.
,
Fuchs
,
S.
,
Geng
,
C.
, and
Pape
,
D.
(
2004
). “
An EMMA and EPG study on token-to-token variability
,”
AIPUK
36
,
47
63
.
54.
Nissen
,
S. L.
, and
Fox
,
R. A.
(
2009
). “
Acoustic and spectral patterns in young children's stop consonant productions
,”
J. Acoust. Soc. Am.
126
,
1369
1378
.
55.
Nordström
,
P.-E.
(
1975
). “
Attempts to simulate female and infant vocal tracts from male area functions
,”
Speech Transm. Lab. Q. Prog. Status Rep.
16
,
20
33
.
56.
Peterson
,
G. E.
, and
Barney
,
H. L.
(
1952
). “
Control methods used in a study of the vowels
,”
J. Acoust. Soc. Am.
24
,
175
184
.
57.
Ramanarayanan
,
V.
,
Tilsen
,
S.
,
Proctor
,
M.
,
Töger
,
J.
,
Goldstein
,
L.
,
Nayak
,
K. S.
, and
Narayanan
,
S.
(
2018
). “
Analysis of speech production real-time MRI
,”
Comput. Speech Lang.
52
,
1
22
.
58.
Riquelme
,
A.
, and
Green
,
L. J.
(
1970
). “
Palatal width, height, and length in human twins
,”
Angle Orthod.
40
,
71
79
.
59.
Rudy
,
K.
, and
Yunusova
,
Y.
(
2013
). “
The effect of anatomic factors on tongue position variability during consonants
,”
J. Speech Lang. Hear. Res.
56
,
137
149
.
60.
Serrurier
,
A.
, and
Badin
,
P.
(
2008
). “
A three-dimensional articulatory model of the velum and nasopharyngeal wall based on MRI and CT data
,”
J. Acoust. Soc. Am.
123
,
2335
2355
.
61.
Serrurier
,
A.
,
Badin
,
P.
,
Boë
,
L.-J.
,
Lamalle
,
L.
, and
Neuschaefer-Rube
,
C.
(
2017
). “
Inter-speaker variability: Speaker normalisation and quantitative estimation of articulatory invariants in speech production for French
,” in
Proceedings of Interspeech 2017
, August 20–24, Stockholm, Sweden, pp.
2272
2276
.
62.
Serrurier
,
A.
,
Badin
,
P.
,
Lamalle
,
L.
, and
Neuschaefer-Rube
,
C.
(
2019a
). “
Characterization of inter-speaker articulatory variability: A two-level multi-speaker modelling approach based on MRI data
,”
J. Acoust. Soc. Am.
145
,
2149
2170
.
63.
Serrurier
,
A.
,
Badin
,
P.
, and
Neuschaefer-Rube
,
C.
(
2019b
). “
Influence of the vocal tract morphology on the F1-F2 acoustic plane
,” in
Proceedings of the 30th Conference on Electronic Speech Signal Processing (ESSV)
, March 6–8, Dresden, Germany, pp.
312
319
.
64.
Shapiro
,
S. S.
, and
Wilk
,
M. B.
(
1965
). “
An analysis of variance test for normality (complete samples)
,”
Biometrika
52
,
591
611
.
65.
Sonnesen
,
L.
,
Petersson
,
A.
,
Berg
,
S.
, and
Svanholt
,
P.
(
2017
). “
Pharyngeal airway dimensions and head posture in obstructive sleep apnea patients with and without morphological deviations in the upper cervical spine
,”
J. Oral Maxillofacial Res.
8
(
3
),
e4
.
66.
Soquet
,
A.
,
Lecuit
,
V.
,
Metens
,
T.
, and
Demolin
,
D.
(
2002
). “
Mid-sagittal cut to area function transformations: Direct measurements of mid-sagittal distance and area with MRI
,”
Speech Commun.
36
,
169
180
.
67.
Sorensen
,
T.
,
Skordilis
,
Z.
,
Toutios
,
A.
,
Kim
,
Y.-C.
,
Zhu
,
Y.
,
Kim
,
J.
,
Lammert
,
A.
,
Ramanarayanan
,
V.
,
Goldstein
,
L.
,
Byrd
,
D.
,
Nayak
,
K.
, and
Narayanan
,
S. S.
(
2017
). “
Database of volumetric and real-time vocal tract MRI for speech science
,” in
Proceedings of Interspeech 2017
, August 20–24, Stockholm, Sweden, pp.
645
649
.
68.
Stevens
,
K. N.
(
2000
).
Acoustic Phonetics
(
MIT
,
Cambridge, MA
).
69.
Story
,
B. H.
,
Vorperian
,
H. K.
,
Bunton
,
K.
, and
Durtschi
,
R. B.
(
2018
). “
An age-dependent vocal tract model for males and females based on anatomic measurements
,”
J. Acoust. Soc. Am.
143
,
3079
3102
.
70.
Thibeault
,
M.
,
Ménard
,
L.
,
Baum
,
S. R.
,
Richard
,
G.
, and
McFarland
,
D. H.
(
2011
). “
Articulatory and acoustic adaptation to palatal perturbation
,”
J. Acoust. Soc. Am.
129
,
2112
2120
.
71.
Tiede
,
M. K.
,
Boyce
,
S. E.
,
Espy-Wilson
,
C. Y.
, and
Gracco
,
V. L.
(
2010
). “
Variability of North American English /r/ production in response to palatal perturbation
,” in
Speech Motor Control: New Developments in Basic and Applied Research
(
Oxford University
,
London
), pp.
53
68
.
72.
Valdés Vargas
,
J. A.
(
2013
). “
Adaptation of orofacial clones to the morphology and control strategies of target speakers for speech articulation
,” Ph.D. thesis,
Université Grenoble Alpes
,
Saint-Martin-d'Hères, France
.
73.
Vilain
,
C.
,
Berthommier
,
F.
, and
Boë
,
L.-J.
(
2015
). “
A brief history of the articulatory-acoustic representation of vowels
,” in
Proceedings of the First International Workshop on the History of Speech Communication Research
, September 6–10, Dresden, Germany.
74.
Vorperian
,
H. K.
,
Wang
,
S.
,
Chung
,
M. K.
,
Schimek
,
E. M.
,
Durtschi
,
R. B.
,
Kent
,
R. D.
,
Ziegert
,
A. J.
, and
Genry
,
L. R.
(
2009
). “
Anatomic development of the oral and pharyngeal portions of the vocal tract: An imaging study
,”
J. Acoust. Soc. Am.
125
(
3
),
1666
1678
.
75.
Vorperian
,
H. K.
,
Wang
,
S.
,
Schimek
,
E. M.
,
Durtschi
,
R. B.
,
Kent
,
R. D.
,
Gentry
,
L. R.
, and
Chung
,
M. K.
(
2011
). “
Developmental sexual dimorphism of the oral and pharyngeal portions of the vocal tract: An imaging study
,”
J. Speech Lang. Hear. Res.
54
,
995
1010
.
76.
Weirich
,
M.
, and
Fuchs
,
S.
(
2011
). “
Vocal tract morphology can influence speaker specific realisations of phonemic contrasts
,” in
Proceedings of the 9th International Seminar on Speech Production (ISSP)
, June 20–23, Montreal, Canada, pp.
251
258
.
77.
Weirich
,
M.
, and
Fuchs
,
S.
(
2013
). “
Palatal morphology can influence speaker-specific realizations of phonemic contrasts
,”
J. Speech Lang. Hear. Res.
56
,
S1894
S1908
.
78.
Weirich
,
M.
,
Fuchs
,
S.
,
Simpson
,
A.
,
Winkler
,
R.
, and
Perrier
,
P.
(
2016
). “
Mumbling: Macho or morphology?
,”
J. Speech Lang. Hear. Res.
59
(
6
),
S1587
S1595
.
79.
Weirich
,
M.
,
Lancia
,
L.
, and
Brunner
,
J.
(
2013
). “
Inter-speaker articulatory variability during vowel-consonant-vowel sequences in twins and unrelated speakers
,”
J. Acoust. Soc. Am.
134
,
3766
3780
.
80.
Winkler
,
R.
,
Fuchs
,
S.
, and
Perrier
,
P.
(
2006
). “
The relation between differences in vocal tract geometry and articulatory control strategies in the production of French vowels: Evidence from MRI and modeling
,” in
Proceedings of the 7th International Seminar on Speech Production (ISSP)
, December 13–15, Ubatuba, Brazil.
81.
Winkler
,
R.
,
Fuchs
,
S.
,
Perrier
,
P.
, and
Tiede
,
M.
(
2011
). “
Speaker-specific biomechanical models: From acoustic variability via articulatory variability to the variability of motor commands in selected tongue mucles
,” in
Proceedings of the 9th International Seminar on Speech Production (ISSP)
, June 20–23, Montreal, Canada, pp.
219
226
.
82.
Wood
,
S.
(
1975
). “
The weaknesses of the tongue arching model of vowel articulation
,” in
Working Papers
(
Lund University
,
Lund, Sweden
), Vol. 11, pp.
55
108
.
83.
You
,
M.
,
Li
,
X.
,
Wang
,
H.
,
Zhang
,
J.
,
Wu
,
H.
,
Liu
,
Y.
,
Miao
,
J.
, and
Zhu
,
Z.
(
2008
). “
Morphological variety of the soft palate in normal individuals: A digital cephalometric study
,”
Dentomaxillofac. Radiol.
37
,
344
349
.
84.
Yunusova
,
Y.
,
Rosenthal
,
J. S.
,
Rudy
,
K.
,
Baljko
,
M.
, and
Daskalogiannakis
,
J.
(
2012
). “
Positional targets for lingual consonants defined using electromagnetic articulography
,”
J. Acoust. Soc. Am.
132
,
1027
1038
.
You do not currently have access to this content.