Jonathan C. Yip
Gestural Coordination in Word-Initial Greek Clusters as
Revealed by Kinematic, Articulatory, and Acoustic Data
Previous studies have shown that gestural timing in consonant clusters is influenced
the order of place of articulation, and manner of articulation (Byrd, 1996; Chitoran et
al., 2002; Chitoran & Goldstein, 2006; Kühnert et al., 2006). However, whether these
effects are due to biomechanical constraints on production, perceptual-recoverability
(acoustic masking) factors, or language-specific patterns—or some combination of
the two–remains controversial.
I Front-to-back clusters have greater gestural overlap than back-to-front clusters
(Byrd, 1996; Chitoran et al., 2002; Chitoran & Goldstein, 2006; Kühnert et al., 2006).
I Plosive+plosive sequences permit less gestural overlap than plosive+liquid sequences
(Chitoran & Goldstein, 2006; Chitoran & Cohn, 2009).
Sample Video Frames
I
Speech Biomechanics
Phonetic gestures are coordinated as action units with critical gestural timings, such
as in the Task Dynamic model (Browman & Goldstein, 1995; Goldstein et al., 2006).
I Gestures involving interdependent articulators (e.g. coronal and dorsal) require
sequential timing, whereas gestures involving independent articulators (e.g. labial and
lingual) may involve greater simultaneity. (Chitoran & Goldstein, 2006; Kühnert et
al., 2006; Chitoran & Cohn, 2009; Bombien et al., 2013).
Figure 1: Top: Ultrasound frames during [kt] from speaker S07 (frames 16.67 ms apart = 60fps).
Bottom: Corresponding lingual contour traces (solid) plotted under traces of the palate (dashed) for
speaker S07. Bold segments along the palate indicate velar (center-left) and alveodental (right) regions for
S07, while gray lines indicate minimal aperture distances between these regions and the lingual contour.
I
Perceptual Recoverability
Acoustic masking occurs when the constriction intervals of C1 and C2 overlap.
I Masking is most likely when C1 and C2 are both plosive, the place of C1 constriction
is posterior to that of C2, and the C1 and C2 constriction intervals overlap (Chitoran
et al., 2002; Chitoran & Cohn, 2009).
I Perceptibility is crucial at word onsets (Marslen-Wilson, 1987; Chitoran et al., 2002).
I
Why Greek?
Modern Greek allows for a large set of CC sequences that minimally differ in C1 and
C2 manner, including labial+coronal sequences [pt ps pl ft] and dorsal+coronal
sequences [kt ks kl xt].
I Each of these clusters occurs in word-initial position with relatively high frequency.
Thus, native Greek speakers are expected to have extensive experience in producing
and perceiving them.
I
RESULTS: C1 RELEASE-BURST ACOUSTICS
RESULTS: ARTICULATORY TIMING (CONT.)
Measure
Constriction lag
C1 Place
[p]<[k]***
Normalized constriction lag
[p]<[k]***
Achievement lag
[p]<[k]***
Normalized achievement lag PlosC2: n.s.
FricC2: [ps]<[ks]*
LatC2: [pl]<[kl]**
Measure
C1 Place
Constriction lag
labial<dorsal***
Normalized constriction lag labial<dorsal***
Achievement lag
labial<dorsal***
Normalized achievement lag PlosC1: n.s.
FricC1: [ft]<[xt]***
C2 Manner
[pt]>[ps]*
[kt]>[ks]**; [kl]>[ks]*
[pt]–[ps]–[pl]: n.s.
[kt]>[ks]***
[pl]>[pt]***; [pl]>[ps]***
[kt]>[ks]***; [kl]>[ks]***
[pl]>[pt]*; [pl]>[ps]***
[kt]>[ks]**
C1 Manner
plosive>fricative***
plosive>fricative***
n.s.
LabC1: [pt]>[ft]***
DorC1: [kt]<[xt]*
Interaction
n.s.
n.s.
n.s.
n.s.
Interaction
n.s.
n.s.
n.s.
C1P×C1M***
Significance codes: 0 ’***’ 0.001 ’**’ 0.01 ’*’ 0.05
Table 1: Results of the LMMs for CC sequences [pt ps pl kt ks kl] (upper half) and [pt ft kt xt]
(lower half), with fixed effects of C1 Place and either C2 Manner or C1 Manner, and random effects
of Speaker and Word.
Figure 2: Camera frames of labial movement during [pt] from speaker S10, with black and white dots
indicating the endpoints of bilabial aperture. Interstitial frames were removed to show constriction
formation and release.
Durational Measures
1. Constriction lag: Duration of the interval from the offset of C1 constriction to
the onset of C2 constriction: Ach2–Rel1.
2. Normalized constriction lag: Constriction lag divided by the duration of the
entire C1-C2 constriction interval: (Ach2–Rel1)/(Rel2–Ach1).
3. Achievement lag: Duration of the interval from the onset of C1 constriction to
the onset of C2 constriction: Ach2–Ach1.
4. Normalized achievement lag: Achievement lag divided by the duration of the
formation of C1 constriction: (Ach2–Ach1)/(Ach1–Ons1).
Synchronous measures of C1 and C2 aperture:
Scatterplots of all data points for C1 and C2 aperture in the labial+coronal and
dorsal+coronal contexts indicate that the C1 and C2 constriction intervals are less
likely to overlap during dorsal+coronal sequences than labial+coronal sequences. For
[kt] and [kl] productions, there are no data points at which both C1 aperture and C2
aperture are simultaneously at or near 0%.
I These data suggest that the tongue is unable to form simultaneous dorsal and
coronal constrictions (but see the next section Results: Lingual Contours for
further discussion).
I
The stability of timing according to speech articulator:
Materials
I
Figure 5: Scatterplots showing the relationship between percent aperture for the C1 gesture (either
labial or dorsal) and percent aperture for the C2 gesture (always coronal). Data are pooled across
speakers, and the times at which each aperture measure was taken are not specified in the plots.
Figure 3: Plots for the acoustic waveform and the movement of the C1 and C2 articulators during the
production of [kt]. Durational measures (shaded boxes): (1) C1 constriction duration, (2) C2 constriction
duration, (3) achievement lag, (4) constriction lag.
Data Collection
Ultrasound images of the tongue were collected using a Zonare z.one mini system.
The transducer (P4-1c phased-array) held in place with an Ultrasound Stabilisation
Headset (Articulate Instruments Ltd).
I Camera images of the lips collected with a miniature NTSC camera, attached via a
attachment arm custom-made for use with the ultrasound stabilization headset.
I
Participants and Task
10 native speakers of Standard Modern Greek recruited at the University of Michigan
(ages 20 to 37). Due to issues with the quality of ultrasound data collected from 2
speakers, articulatory and acoustic data from only 8 speakers were analyzed.
I Speakers read randomized target words in the Greek carrier phrase ["i.pa
kai "pa.li].
5 reps. of [pt ps ft kt ks xt] + 6 reps. of [pl kl] = 174 utterances per speaker.
I
RESULTS: ARTICULATORY TIMING
Linear mixed-effects modeling (LMM, Baayen, 2008) of the articulatory timing data
reveal a main effect of C1 Place for all C1 and C2 manners. Gestural overlap was
common in labial+coronal [pt ps pl ft], and constriction lag was 36±4 ms longer in
dorsal+coronal [kt ks kl xt] than in labial+coronal [pt ps pl ft] (F[1,168]=150.09,
p<0.0001).
I In terms of the effects of C1 and C2 manner, constriction lag was 24±5 ms
longer in plosive+plosive [pt kt] than in fricative+plosive [ft xt] (F[1,168]=150.09,
p<0.0001), and, in the dorsal+coronal context, plosive+fricative [ks] exhibited 12±5
ms shorter lag than plosive+plosive [kt] (t=3.175, p=0.0018) and 12±7 ms shorter
lag than plosive+lateral [kl] (t=2.578, p=0.0108).
I
DATA ANALYSIS
Smoothing Spline ANOVAs (SSANOVA, Davidson, 2006) on the lingual contour data
for sequences taken at the C1-constriction midpoint reveal differences across speakers
in the relationship between C2 manner and tongue position in dorsal+coronal (i.e.
lingual+lingual) contexts.
I In [ks], the C1 and C2 constrictions are often co-produced. At the midpoint of C1
([k]) closure, the anterior (post-apical) portion of the tongue moves closer toward the
palate when C2 manner is fricative than when it is plosive or lateral, for 6 out of 8
speakers (S01, S03, S05, S07, S08, and S10). A corresponding pattern is evident in
the LMM results for constriction lag (refer to the previous section Results:
Articulatory Timing).
I The articulation of [s] may involve a longer region of constriction along the palate
than that of [t] and [l]. This difference in constriction place may correspond with to
increased perceptibility of acoustic cues to [s]: a longer constriction channel may
increase spectral amplitudes and lower the energy frequencies in [s], thus making [s]
more acoustically different from [T] (the only other voiceless coronal fricative in
Greek).
I
I
The 14th Conference on Laboratory Phonology, July 25–27, 2014, Tokyo, Japan
Figure 4: Mean durations for C1 constriction (light gray bars) and temporally-aligned durations of C2
constriction (black bars) in the CC sequences [pt ps pl ft kt ks kl xt]. Intervals of C1-C2 overlap are
shown as dark gray sections, while C1-to-C2 constriction lag is shown as white spaces between the two
constriction intervals.
I
The robust effect of longer lag between C1 and C2 gestures in dorsal+coronal
sequences than in labial+coronal sequences can be readily explained in terms
of the relative interdependence between the articulators.
I
For dorsal+coronal sequences, where the two gestures are interdependent, the
time needed to move from one constriction to the next is relatively long
because the dorsal and coronal constrictions cannot be made simultaneously.
I
It is important to note that speakers do not exhibit the same level of contrast
in constriction lag according to C1 place–some speakers seldom produced
constriction overlap between C1 and C2. This may be, in part, due to
differences between speakers in the rate of speech and the shape and size of
the articulators.
RESULTS: LINGUAL CONTOURS
Analysis Procedures
Lingual Data: Tongue-contour splines were drawn with Articulate Assistant
Advanced software (AAA, by Articulate Instruments Ltd), and aperture was
measured as the shortest distance from the tongue trace to the coronal and dorsal
regions of the palate (defined separately according to speaker).
I Labial Data: Labial aperture was measured with AAA as the midsagittal distance
between the lips during gestures for [p], or the midsagittal distance between the lower
lip and the highest position of the lip against the upper front incisors during gestures
for [f].
I Acoustic Data: Acoustic durations of bilabial and velar plosive release bursts in [pt
pl kt kl] were measured in Praat (Boersma & Weenink, 2012). Because the interval
of release burst of a C1 plosive is masked by concurrent aperiodic noise during a C2
fricative, C1 release-burst measures for plosive+fricative [ps ks] were omitted.
Pooled acoustic measures of plosive release bursts in sequences [pt pl kt kl] reveal a
positive correlation between the duration of constriction lag and the duration of C1
release burst, but only in labial+coronal contexts. Spectral moment frequency was
also postively correlated with constriction lag, but only for plosive+plosive
labial+coronal [pt].
I Plots for burst duration and spectral moment also indicate that the acoustic
properties of [p] and [k] release bursts overlap more frequently when C2 manner is
plosive rather than lateral.
I Interestingly, shorter durations of constriction lag in [pt pl] result in greater degrees
of durational and spectral contrast between [p] and [k] release bursts, with a major
limitation being that release-burst durations of 0 ms would render [p] inaudible.
I
CONCLUSIONS
EXPERIMENTAL DESIGN
5 words for each onset cluster [pt ps ft kt ks xt] and 2 words for each plosive+lateral
cluster [pl kl]. Each cluster was followed by either of the front vowels [i, e], in order to
reduce any variation in articulatory timing due to changes in vowel context.
I Sample target words:
Labial+Coronal
Dorsal+Coronal
pt ["pti.si] πτήση ’flight’
kt ["kti.ma] κτήμα ’estate’
ps ["psi.fos] ψήφος ’vote (n.)’
ks ["kse.Ro] ξέρω ’(I) know’
pl ["ple.on] πλέον ’more’
kl ["kli.ma] κλίμα ’climate’
ft ["fte.o] φταίω ’(I) am at fault’ xt ["xte.ni] χτένι ’scallop’
Figure 7: Scatterplots showing the relationship between constriction lag duration and C1 release-burst
duration (top plots) and between constriction-lag duration and the spectral moment of the C1 release
burst (bottom plots).
Speech Biomechanics
Consonant Clusters
DATA ANALYSIS (CONT.)
Figure 6: SSANOVA results for the lingual contours extracted at the midpoint of C1 constriction during
dorsal+coronal sequences [kt ks kl xt], by speaker. In each plot, the front of the tongue is situated on the
right, and the back of the tongue is on the left. Note that the x- and y-axes are scaled differently in each
plot, as talkers have different tongue shapes and sizes.
e-mail: [email protected]
Perceptual Recoverability
BACKGROUND
*Department of Linguistics, The University of Hong Kong
Department of Linguistics, University of Michigan, Ann Arbor
The influence of perceptibility on gestural timing:
I
In contexts involving fricative manner, overlap between C1 and C2 is likely to
occur, although this varies by speaker. In [ks] contexts, a retraction and
lengthening of the place of anterior constriction along the palate may result in
improved perceptibility of C2 ([s]).
I
The higher likelihood of gestural overlap in sequences containing fricatives may
be due to the fact that the critical cues to fricatives appear during gestural
constriction rather than during movements into and out of constriction.
I
Under certain conditions, gestural overlap and/or co-production may enhance
perceptibility, especially when increased coarticulatory behavior results in a
larger acoustic constrastiveness, as is the case with [s]-frication in [ks] and
[p]-release bursts in [pt ps pl].
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http://www-personal.umich.edu/∼jonyip