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:

– Maximize the distinctiveness of contrasts

– Minimize articulatory effort

– Maximize the rate of information transmission

Auditory, visual systems

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):

• Some languages have free variation between coronal and velar before lateral (but contrast elsewhere), e.g. Bolton English (Shorrocks 1998), Mong Njua (Lyman 1974)

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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 + fricationFormant transitions

burstformant transitions

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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.

b d g _r brown drown ground _l blow glow _V bid did gig

• Sentence frame ‘Say X to me’• Presented twice in random order• 5 native speakers of American English, 4 female, 1 male.

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

bl bursts

gl bursts

• Burst peak: amplitude peak of the burst spectrum

• Amid-Ahi (cf. Suchato et al 2005)

•Amid = average amplitude from 1.25 kHz - 3 kHz

•Ahi = average amplitude from 3.5 kHz - 8 kHz

mid high

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.

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Stop-[l] clusters - formants

• Stops are not well differentiated by formant transitions before [l].

Formant onsets

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Formant onsets

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• 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.

Stop-[l] clusters - formants

• Stops are not well differentiated by formant transitions before [l].

• Similar results from a preliminary study of Hebrew initial [bl-, dl-, gl-], [pl-, tl-, kl-] clusters:• F2 and F3 onsets are very close to steady state values

for [l] for all places of articulation.• except F3 is somewhat lower after [b] compared to [d,

g].• Stops appear to be overlapped with following lateral, so

formants are onset are largely determined by [l].• Effect is particularly striking for English [-dl-], since [d] is usually

characterized by relatively high F2 at release.• Possibly lateral release of [d] results in a lower F2 onset.

Stop-l clusters - burst

• [gl] is more compact than [bl].

• [gl] has a longer burst than [bl].

* p < 0.01

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• [gl] burst has a higher frequency peak than [bl] burst.

Amid-Ahi

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• Initial [bl-, gl-] clusters are distinguished by burst quality and duration.

Stop-l clusters - burst

• Medial [-dl-, -gl-] are also differentiated by their bursts.• But the properties of [-dl-] bursts deviate substantially

from prevocalic [d] bursts in the direction of [g]/[gl] bursts.

burst duration

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Lateral release

• The properties of the [dl] burst are expected consequences of laterally releasing [d].

• Centrally released [d] burst has significant high frequency energy because it is filtered by the short cavity in front of the alveolar closure.

• But with lateral release, the front cavity includes the side passages opened up by lowering the sides of the tongue, and thus is significantly longer.

• Hence lower frequency peak, more compact burst shape.

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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-]

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(ba)dly (Ba)gleyTime (s)

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glee

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Restrictions on coronal-lateral clusters

• Hebrew contrasts initial [bl, dl, gl], [pl, tl, kl].

dl

gl

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Time (s)0.120813 0.320904

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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 distinct than pre-r, pre-V.

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?

bl(ow)Time (s)0.350678 0.470090

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br(ew) dr(ew) gr(ew)

br vs. dr vs. gr - Formants

• Formant transitions distinguish [br, dr, gr].

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Formant onsets

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br vs. dr vs. gr - burst

• burst distinguishes [br, dr, gr]

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