Stop Place Contrasts before
Liquids
Edward Flemming
MIT
Is there a biological grounding of phonology?
• Phonetic/phonological systems are shaped by the
need to support rapid, robust communication,
• …given the limits of our speech
production/perception apparatus.
• Biology imposes constraints on phonology.
• Efficient communication:
Auditory, visual
– Maximize the distinctiveness of contrasts
systems
– Minimize articulatory effort
– Maximize the rate of information transmission
Vocal tract,
motor control,…
Restrictions on coronal-lateral clusters
• A case study adopting this approach: Stop place
contrasts before liquids.
• Many languages allow [pl, kl]/[bl, gl] clusters, but
exclude initial [tl, dl] (Kawasaki 1982).
• E.g. English, German, Norwegian, Thai, etc
• English:
 [b-d-g, p-t-k] contrast before [r], brew-drew-grew, pry-try-cry
 [b-g, p-k] contrast before [l], blue-glue, plan-clan
 initial [dl-, tl-] are not possible.
Restrictions on coronal-lateral clusters
• This is a result of a dispreference for coronal-dorsal stop
contrasts before laterals (Flemming 1995).
• Some languages reverse the English pattern,
 [tl-, dl-] OK, but no *[kl-, gl-].
• e.g. Haroi and other Chamic languages (Mudhenk & Goschnick
1977), Katu dialects (Wallace 1969):
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
• Some languages have free variation between coronal and
velar before lateral (but contrast elsewhere), e.g. Bolton
English (Shorrocks 1998), Mong Njua (Lyman 1974)
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Restrictions on coronal-dorsal contrasts before [l]
• Kawasaki (1982) hypothesizes that this dispreference is due to
perceptual similarity of [dl-gl], [tl-kl].
• General hypothesis: preferred clusters are those in which all contrasts
are perceptually distinct (cf. Ohala 1992, Steriade 1999, Wright 2004,
etc).
 Before [l], contrasts between coronal & dorsal stops are not very
distinct.
Evidence:
• Kawasaki (1982): Evidence from 1 speaker that formant transitions are
very similar in [dl-, gl-].
- But bursts can be sufficient to distinguish stops.
• Hallé, et al (1998), Hallé & Best (2007):
- French listeners identify (illegal) [dl-, tl-] as [gl-, kl-] respectively.
- French and Am. English listeners have difficulty discriminating
Hebrew [dl-gl] and [tl-kl] contrasts.
Restrictions on coronal-dorsal contrasts before [l]
• Further investigate Kawasaki’s hypothesis through acoustic
analysis of American English and Hebrew.
• Would English [dl-gl] and [tl-kl] contrasts be less distinct
than stop place contrasts before [r] (and vowels)?
• How do we infer the expected realization of [dl-, tl-]?
• Other stop-liquid clusters
• Medial [-dl-, -tl-] clusters
• [tl-, dl-] in languages that allow these clusters (e.g. Hebrew,
Russian).
• But NB languages that allow these contrasts may realize stop-liquid
clusters in a different fashion, e.g. less gestural overlap.
Cues to stop place contrasts
• Prevocalic stops (e.g. Dorman et al 1977):
 Release burst - transient + frication
 Formant transitions
burst
formant
transitions
5000
0
26.1405
26.5479
Time (s)
Materials
• 6 near-minimal triplets for br-dr-gr
• 6 near-minimal pairs for bl-gl
• 9 triplets for [b, d, g], each preceding the same set of nine
vowels.
_r
_l
_V
b
brown
blow
bid
d
drown
did
g
ground
glow
gig
• Sentence frame ‘Say X to me’
• Presented twice in random order
• 5 native speakers of American English, 4 female, 1 male.
5000
5000
0
0.350678
0.47009
0
0.312515
Time (s)
bl(ow)
5000
0.487222
Time (s)
gl(ow)
5000
0
0.322387
0.522607
Time (s)
br(ew)
5000
0
0.337107
0.537411
Time (s)
dr(ew)
0
0.352544
0.552427
T ime (s)
gr(ew)
Quantifying burst shape
• Measured from smoothed spectra (Hanson & Stevens
2003)
 Calculate a series of seven DFTs on 3 ms windows at 1 ms
intervals.
 Average these spectra.
Quantifying burst shape
• Burst peak: amplitude
peak of the burst
spectrum
bl bursts
• Amid-Ahi (cf. Suchato et al
mid
gl bursts
high
2005)
•Amid = average
amplitude from 1.25
kHz - 3 kHz
•Ahi = average
amplitude from 3.5
kHz - 8 kHz
Measurements
Burst:
• Burst duration - from stop release to onset of first formant.
• Usually coincides with onset of voicing, but weakly voiced
frication is included in the burst.
Formants:
• Measured F2 and F3 at the end of the burst, or the onset of formants.
5000
br
0
58.0934
58.1442
58.1686
58.1755
Time (s)
58.2355
br vs. dr vs. gr - Formants
Formant onsets
2500
2000
Hz
1500
* *
*
1000
500
0
F2
F3
• Formant transitions
distinguish [br, dr, gr].
br
dr
gr
* p < 0.01
br vs. dr vs. gr - burst
Amid-Ahi
burst duration (ms)
*
15
dB
0.05
10
5
frequency of peak
*
0.04
br
dr
*
0.03
0.02
gr
1000
500
0.01
• burst distinguishes [br, dr, gr]
* p < 0.05
*
1500
0
0
*
2000
Hz
20
burst duration
0
br
dr
*
gr
br
dr
*
gr
bl vs. gl - formants
Formant onsets
3500
3000
Hz
2500
2000
bl
gl
1500
1000
500
0
F2
F3
• Formant transitions
do not differentiate
[bl] from [gl].
bl vs. gl - burst
Amid-Ahi
burst duration (ms)
*
15
dB
35
10
5
2000
*
30
25
1500
20
Hz
20
15
10
gl
• [gl] is more
compact than [bl].
*
1000
500
5
0
0
0
bl
frequency of peak
burst duration
bl
gl
• [gl] has a longer
burst than [bl].
* p < 0.01
bl
gl
• [gl] burst has a
higher frequency
peak than [bl]
burst.
Summary
• [br, dr, gr] are distinguished by formant transitions and
burst quality in much the same way as prevocalic stops.
• [bl, gl] are distinguished by burst quality, but not formant
onsets.
Stop-[l] clusters
• Stops are not well differentiated by formant transitions
before [l].
• Initial [bl-, gl-]
• No significant differences
in formant onsets.
• Medial [-dl-, -gl-]
• Small differences in F2 onsets
• -dl- seems to allow more coarticulatory
influence of a preceding front vowel.
Formant onsets
3500
3500
3000
3000
2500
2500
bl
gl
2000
1500
1000
Hz
Hz
Formant onsets
1500
1000
500
500
0
0
F2
F3
dl
gl
2000
F2
F3
Medial [-dl-] vs. [-gl-]
•
•
•
•
•
3 speakers from the previous study
Near-minimal pairs, e.g. wrigley-ridley, badly-Bagley.
Same measures as before.
Clusters are differentiated primarily by burst quality
Small differences in F2, F3 onsets
• -dl- seems to allow more coarticulatory influence of a preceding
front vowel.
frequency of peak
Amid-Ahi
burst duration
2500
20
2000
25
15
15
10
1500
Hz
20
dB
burst duration (ms)
30
10
500
5
5
0
0
0
dl
gl
1000
dl
gl
dl
gl
Comparison to prevocalic stops
Burst spectrum:
• [b] - low frequency
peak
• [bl] is similar.
 Sometimes additional
peak ~3000 Hz (F3 or
F4)
• [g] generally has a
prominent peak <
5000 Hz, frequency
dependent on
following vowel.
• [gl] has a peak at
~1300 Hz, cf. goal
d-
40
40
–30
0
–30
0
40
2500
Hz
-dl-
2500
Hz
5000
5000
40
goal
-gl-
–30
–30
0
40
2500
Hz
5000
0
2500
Hz
5000
Summary
• Stop place contrasts are distinguished by burst
characteristics and formant transitions in stopliquid clusters.
• Both types of cues appear to be comparable to
prevocalic cues to stop place in most cases.
• The perceptual significance and relative weight of
these cues remains to be assessed.
Restrictions on coronal-lateral clusters
• Preliminary study of medial [-dl-,-gl-] in English
- difference in formant transitions in some contexts.
- difference in burst spectrum (Peak: [dl] 1579 Hz, [gl] 1177 Hz)
- but medial [-gl-] is a bit different from initial [gl-]
5000
5000
0
0.276954
5000
0
0.524867
0.278185
Time (s)
(ba)dly
0
0.499791
0.000422777
Time (s)
(Ba)gley
0.2216
Time (s)
glee
Restrictions on coronal-lateral clusters
• Hebrew contrasts initial [bl,
dl, gl], [pl, tl, kl].
5000
40
dl
–30
0
0.140447
5000
0
1000
2000
0.335739
3000
4000
5000
Frequency (Hz)
6000
7000
8000
Time (s)
40
gl
–30
0
0
0.120813
0.320904
Time (s)
1000
2000
3000
4000
5000
Frequency (Hz)
6000
7000
8000
Introduction
• A case study adopting this approach: Stop place
contrasts before liquids.
Background:
• All languages allow stop place contrasts before
vowels.
• Many languages permit word-initial stop place
contrasts before liquids. E.g. English:
 [b-d-g] contrast before [r], brew-drew-grew
 [b-g] contrast before [l], blue-glue
• In some languages, stop-liquid clusters are the
only onset clusters, e.g. Spanish.
Introduction
Structure:
• Dispreference for dl-gl
• Theory: insufficiently distinct.
• Evidence: other stop-l clusters, medial, other lgs, Tr clusters for
comparison (3-way contrast).
• Cues to stop place: burst, formant transitions
• Measures
• What’s wrong with dl-gl?
• Tl clusters not differentiated by formants
– English initial, medial, Hebrew initial
– compare Tr clusters
– Why? coproduction with (velarized) [l] - normal for b, g, not for d
• Tl clusters are differentiated by burst durn, quality
– but [dl] bursts are non-canonical, shifted towards velars
• So 3 way contrast would have to be realized by burst - less
Introduction
Two questions:
• Why are stop-liquid clusters preferred onset
clusters?
• Why are [tl-kl], [dl-gl] contrasts dispreferred?
Hypotheses:
• Preferred clusters are those in which contrasts are
perceptually distinct.
• Stop place is generally well-cued before liquids.
• But coarticulatory effects render coronal and velar
stops perceptually similar before [l] (Kawasaki 1982).
Introduction
• The preference for stop-liquid clusters is often attributed to
a preference for large sonority rise between consonants in
an onset.
• Alternative: preferred clusters are those in which all
contrasts are perceptually distinct (cf. Ohala 1992, Steriade 1999,
Wright 2004, etc)
• High sonority of liquids is relevant only because more
sonorous sounds are generally better able to support the
realization of cues to adjacent consonants.
• This line of analysis can be extended to account for
restrictions that are unrelated to sonority: dispreference for
coronal-velar contrasts before laterals.
The present study
• Investigate acoustic properties that could serve as cues to
stop place contrasts in stop-liquid clusters, using American
English as a case study.
• Many languages permit stop place contrasts before liquids.
E.g. English:
 [b-d-g] contrast before [r], brew-drew-grew
 [b-g] contrast before [l], blue-glue
 initial [dl-] is not possible.
• What is the nature of cues to place in this position? How
doe they compare to place cues in prevocalic position?
• Why are liquids good contexts for stop place contrasts?
• Why is the pre-[l] context not as good as the prevocalic
context?
 Specifically, why are [dl-gl]/[tl-kl] contrasts often excluded?