THE EFFECT OF PALATE MORPHOLOGY ON CONSONANT ARTICULATION IN HEALTHY ...

70 Pages·2011·0.48 MB·English

THE EFFECT OF PALATE MORPHOLOGY ON CONSONANT ARTICULATION IN
HEALTHY SPEAKERS

by

KRISTA RUDY

A thesis submitted in conformity with the requirements for the degree of M.Sc.
Graduate Department of Speech-Language Pathology
University of Toronto

© by Krista Rudy (2011)
ABSTRACT
The Effect of Palate Morphology on Consonant Articulation in Healthy Speakers
Krista Rudy
Masters of Science, 2011
Department of Speech-Language Pathology
University of Toronto
This study investigated the effect of palate morphology and anthropometric measures of
the head and face on lingual consonant target (positional) variability of twenty one adult speakers
(eleven male, ten female). An electromagnetic tracking system (WAVE, NDI, Canada) was used
to collect tongue movements while each speaker produced a series of VCV syllables containing a
combination of consonants /t, d, s, z, , t , k, g, j/ and three corner vowel /i, , u/. Distributions of
x, y, and z coordinates representing mʃaxʃimum tongue elevation during the cɑonsonants were used
to represent target variability across contexts. Palate and anthropometric measures were
obtained for each participant. A correlational analysis showed that target variability of the
consonants produced in the front of the mouth (e.g. alveolar and palatal) was explained, to a
degree, by palate morphology. The variability of velar consonants was not explained by the
structural measures.
ii
“Develop a passion for learning. If you do, you will never cease to grow.”
Anthony J. D’angelo

iii
ACKNOWLEDGEMENTS
To my supervisor, Dr. Yana Yunusova: You have been an extremely influential and positive
figure in my life over the last two years. Throughout this process, you have challenged me,
inspired me to work hard, and provided me with the guidance and encouragement necessary to
continue through times of adversity. Your mentorship has afforded me with lessons that will
continue to influence my future academic, professional and personal life. For this, I am so
thankful.
To the members of my supervisory committee, Dr.’s Pascal van Lieshout and John
Daskalogiannakis: I sincerely thank you for your feedback, discussions, and thought-provoking
questions, which challenged me to think about this research from different perspectives.
To my dearest friend, Adrienne Chan: You have always been one of my greatest supporters in
all aspects of my life. I cannot thank you enough, nor find the words that would adequately
convey how important your support has been to the completion of this project.
Finally, I would like to thank my parents, Robert and Deborah Rudy, and my brothers: I owe all
of my achievements to you. Thank you for your unconditional love and support. Without your
faith in me, and your determination to never give up on me, this would not have been possible,
thank you so much.

iv
TABLE OF CONTENTS
Abstract............................................................................................................................................ii
Acknowledgements.........................................................................................................................iv
Table of Contents.............................................................................................................................v
List of Tables.................................................................................................................................vii
List of Figures...............................................................................................................................viii
Introduction......................................................................................................................................1
Sources of Articulatory Variability......................................................................................2
The Hard Palate and Structures of the Head and Face….....................................................3
The Hard Palate as a Source of Articulatory Variability………………………………….5
Limitations of the Previous Research..................................................................................9
Questions and Hypotheses of the Present Study…............................................................11
Method...........................................................................................................................................12
Participants.........................................................................................................................12
Speech Sample...................................................................................................................13
Data Acquisition and Processing.......................................................................................14
Measurements....................................................................................................................15
Target Variability Measures..................................................................................17
Structural Measures: Palate Measures...................................................................18
Structural Measures: Anthropometric Measures...................................................20
Statistical Analysis.............................................................................................................23
Results............................................................................................................................................25
Structural Measures...........................................................................................................25
Anthropometric Measures......................................................................................25
Palate Measures.....................................................................................................29
v
Correlations between Structural Measures........................................................................32
Target Variability Measures..............................................................................................33
Correlations between Structural Measures and Target Variability Measures...................35
Discussion......................................................................................................................................39
Structural Measures: Anthropometric and Palate Measures.............................................39
Target Variability Measures..............................................................................................42
Palate Measures and Target Variability.............................................................................45
Palate Measures and Spread...............................................................................................47
Anthropometric Measures and Target Variability.............................................................48
Conclusions........................................................................................................................49
Limitations.........................................................................................................................50
References......................................................................................................................................53

vi
LIST OF TABLES
Table 1 Participant demographics.......................................................................................13
Table 2 Reliability and precision of anthropometric measures...........................................23
Table 3 Descriptive statistics of anthropometric measures.................................................25
Table 4 Correlation matrix of anthropometric measures....................................................27
Table 5 Descriptive statistics of palate measures................................................................29
Table 6 Correlation matrix of palate measures...................................................................31
Table 7 Correlation matrix of structural measures..............................................................32
Table 8 Descriptive statistics of variability measures.........................................................34
Table 9 Correlation matrix of structural and tongue blade variability measures................35
Table 10 Correlation matrix of structural and tongue dorsum variability measures............36

vii
LIST OF FIGURES
Figure 1 Equipment set up....................................................................................................15
Figure 2 Kinematic and acoustic signal display...................................................................16
Figure 3 Positional data of lingual variability......................................................................18
Figure 4 Hard palate landmarks...........................................................................................19
Figure 5 Head and face landmarks.......................................................................................22
Figure 6 Box and whisker plots of anthropometric measures..............................................26
Figure 7 Anthropometric measures scatterplots...................................................................27
Figure 8 Scatterplot matrix of anthropometric measures.....................................................28
Figure 9 Box and whisker plots for palate measures............................................................30
Figure 10 Histogram of palate curvature variable..................................................................30
Figure 11 Scatterplot matrix of palate measures....................................................................31
Figure 12 Scatterplots of structural measures........................................................................33
Figure 13 Box and whisker plots of variability measures......................................................34
Figure 14 Scatterplots of palate curvature and variability measures......................................37
Figure 15 Scatterplots of palate and variability measures......................................................37
Figure 16 Barplot of 3D variability for speakers with flat and domed palates......................38
viii
1

INTRODUCTION
Variability is a consistent feature of all motor behaviours. Motor variability provides
information about how the brain controls motor tasks. High variability might indicate that a
performed task is new to the learner (Muller & Sternad, 2004). As an individual becomes more
proficient with the motor task, variability seems to decrease and movement becomes more
consistent and stable (Fletcher, 1989; Handford, 2006; Newell, Deutsch, Sosnoff and Mayer-
Kress, 2006). Motor variability differs with age; children tend to have more variable motor
behaviours than adults (Cheng, Murdoch, Goozee and Scott, 2007; Riely & Smith, 2003). Motor
variability also conveys information about the integrity of the motor control system. For
example, motor dysfunction (e.g., in neurodegenerative diseases) is generally associated with
abnormal levels of motor variability (Anderson, Lowit and Howell, 2008; Cheng et al., 2007;
Kleinow, Smith and Ramig, 2001).
For many years, studies investigating motor control in speech production sought to
uncover invariant features in a speech signal (Fujimura, 1986). However, speech is inherently
variable. For example, articulator positions achieved for different sounds obtained using
kinematic approaches show notable variability across repetitions (Alfonso & Van Lieshout,
1997; Cheng et al., 2007; Dromey & Sanders, 2009; Kleinow et al., 2001; Perkell & Nelson,
1985).
A number of studies have investigated target (positional) variability in speech, yet not
enough is known about normal (expected) target variability during sound production (Van
Lieshout & Namasivayam, 2010). Among sound classes, motor variability during consonant
articulation is particularly understudied. For example, one of the influential models of speech
2

production, DIVA (Directions into Velocities of Articulators), models consonants as it does
vowels (Guenther, 1995); in fact, it can only effectively model a small number of consonants
consisting of mostly voiced stops. Understanding normal target variability in consonant
production is necessary to inform theories of speech motor control and to enable the
development and expansion of comprehensive speech production models which encompass
different sound classes. There are also important clinical implications for quantifying normal
consonant target variability. Normal ranges of consonant target variability may provide
clinicians with a reference with which to appropriately interpret instrumental assessment of
neurological speech disorder (Higgins, Carney and Schulte 1994; McAuliffe, Ward and
Murdoch, 2001). In addition, quantifying normal consonant target variability and identifying its
sources may provide valuable information that is applicable to the development of treatment
tools for speech therapy, focused on the use of visual information to train speech movements.

Sources of Articulatory Variability
There are a number of potential sources of articulatory variability in speech that have
been identified. These sources include neural noise (Latash, Scholz and Schoner, 2002; Manoel
& Connolly, 1995; Muller & Sternad, 2004), motor equivalence (Abbs & Gracco, 1984; Hughs
& Abbs, 1976; Lindblom, 1983; Perkell, Matthies, Svirsky and Jordan, 1993), the quantal nature
of the relationship between acoustics and kinematics (Perkell, 1997; Perkell & Nelson, 1985;
Stevens, 1980), as well as linguistic and prosodic factors (Gay, 1977; Gay, 1974; Guenther,
1995; Liberman & Mattingly, 1985; Lindblom, 1990; Perkell, Zandipour, Matthies and Lane,
2002). Anatomical differences between speakers have emerged as a source of articulatory