Stop Place Contrasts before Liquids

1. Stop Place Contrasts before Liquids Edward Flemming MIT

2. 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,…

3. 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.

4. 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)

5. 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.

6. 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.

7. Cues to stop place contrasts • Prevocalic stops (e.g. Dorman et al 1977): • Release burst - transient + frication • Formant transitions formant transitions burst

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

9. 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.

10. Quantifying burst shape • 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 bl bursts mid high gl bursts

11. br 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.

12. Stop-[l] clusters - formants • Stops are not well differentiated by formant transitions before [l]. • Medial [-dl-, -gl-] • Small differences in F2 onsets • -dl- seems to allow more coarticulatory influence of a preceding front vowel. • Initial [bl-, gl-] • No significant differences in formant onsets.

13. 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.

14. * * * Stop-l clusters - burst • Initial [bl-, gl-] clusters are distinguished by burst quality and duration. • [gl] is more compact than [bl]. • [gl] burst has a higher frequency peak than [bl] burst. • [gl] has a longer burst than [bl]. * p < 0.01

15. 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.

17. 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. Fant 1960

18. 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-] (Ba)gley glee (ba)dly

19. Restrictions on coronal-lateral clusters • Hebrew contrasts initial [bl, dl, gl], [pl, tl, kl]. dl gl

20. 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.

21. 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.

22. 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).

23. 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.

24. 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?

25. bl(ow) gl(ow) br(ew) dr(ew) gr(ew)

26. * * * br vs. dr vs. gr - Formants • Formant transitions distinguish [br, dr, gr]. * p < 0.01

27. * * * * * * * br vs. dr vs. gr - burst • burst distinguishes [br, dr, gr] * p < 0.05