Stop Place Contrasts before LiquidsEdward FlemmingMIT

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 contrastsMinimize articulatory effortMaximize the rate of information transmissionAuditory, visual systemsVocal tract, motor control,

Restrictions on coronal-lateral clustersA 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, etcEnglish:[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-claninitial [dl-, tl-] are not possible.

Restrictions on coronal-lateral clustersThis 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)

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.Hall, et al (1998), Hall & 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 Kawasakis 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 clustersMedial [-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 contrastsPrevocalic stops (e.g. Dorman et al 1977):Release burst - transient + fricationFormant transitionsburstformant transitions

Materials6 near-minimal triplets for br-dr-gr6 near-minimal pairs for bl-gl9 triplets for [b, d, g], each preceding the same set of nine vowels.Sentence frame Say X to mePresented twice in random order5 native speakers of American English, 4 female, 1 male.

b

d

g

_r

brown

drown

ground

_l

blow

glow

_V

bid

did

gig

Quantifying burst shapeMeasured 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 shapebl burstsgl burstsBurst peak: amplitude peak of the burst spectrumAmid-Ahi (cf. Suchato et al 2005)Amid = average amplitude from 1.25 kHz - 3 kHzAhi = average amplitude from 3.5 kHz - 8 kHzmidhigh

MeasurementsBurst: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.

Stop-[l] clusters - formantsStops 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.

Stop-[l] clusters - formantsStops 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[gl] burst has a higher frequency peak than [bl] burst.

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

Stop-l clusters - burstMedial [-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.

Lateral releaseThe 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.Fant 1960

Restrictions on coronal-lateral clustersPreliminary study of medial [-dl-,-gl-] in Englishdifference 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-](ba)dly(Ba)gleyglee

Restrictions on coronal-lateral clustersHebrew contrasts initial [bl, dl, gl], [pl, tl, kl].dlgl

IntroductionA 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-glueIn some languages, stop-liquid clusters are the only onset clusters, e.g. Spanish.

IntroductionStructure:Dispreference for dl-glTheory: insufficiently distinct.Evidence: other stop-l clusters, medial, other lgs, Tr clusters for comparison (3-way contrast).Cues to stop place: burst, formant transitionsMeasuresWhats wrong with dl-gl?Tl clusters not differentiated by formantsEnglish initial, medial, Hebrew initialcompare Tr clusters Why? coproduction with (velarized) [l] - normal for b, g, not for dTl clusters are differentiated by burst durn, qualitybut [dl] bursts are non-canonical, shifted towards velarsSo 3 way contrast would have to be realized by burst - less distinct than pre-r, pre-V.

IntroductionTwo 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).

IntroductionThe 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 studyInvestigate 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-glueinitial [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)gl(ow)br(ew)dr(ew)gr(ew)

br vs. dr vs. gr - FormantsFormant transitions distinguish [br, dr, gr].* p < 0.01

br vs. dr vs. gr - burstburst distinguishes [br, dr, gr]

* p < 0.05