The Phonetics and Phonology of Nasal Gestures Patrice Speeter Beddor University of Michigan Supported by NSF

The Phonetics and Phonology ofNasal Gestures

Patrice Speeter BeddorUniversity of Michigan

Supported by NSF

Anthony Brasher

Rose Letsholo

Susan Lin

Chandan Narayan

Chutamanee Onsuwan

Samantha Sefton

In collaboration with:

Background

The temporal and spatial extent of coarticulatory vowel nasalization is known to be highly variable in ways that depend on phonetic context and prosodic structure, including, among many other factors:

obstruent voicing in NC clusters (Malécot, 1960)

frication in NC clusters (Ohala & Busà, 1995; Busà, 2007)

vowel length (Whalen & Beddor, 1989)

syllable structure (Krakow, 1989; Cohn, 1990; Solé, 1995)

stress (Vaissière, 1988; Krakow, 1993)

Central hypothesis

Hypothesis: The temporal and spatial extent of the nasal gesture is relatively constant across a range of contextual conditions, although the temporal alignment of nasal and oral gestures can differ across contexts in predictable ways.

Three-pronged approach: production, perception, phonology

For several years, cross-language research on coarticulatory variation in our lab has been motivated by the expectation that the nasal (lowered velum) gesture is more stable than might appear from the vowel nasalization literature.

Central hypotheses

Production: In tautosyllabic VN sequences, duration of coarticulatory V nasalization and duration of N co-vary, such that velum lowering in the syllable rhyme is relatively stable across phonetic

contexts.

Investigated for 2 VN contexts: following C voicing

preceding V length

Phonology: The co-variation between V and N in production and perception is consistent with widely attested phonological patterns.

~

Perception: Listeners treat N and V as perceptually equivalent and are more sensitive to total nasalization in the rhyme than to the precise

alignment of oral and nasal gestures.

~

Time (s)1.76593 2.07034

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0.2169

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Variation in temporal alignment

Oral closure

Vowel Loweredvelum

Same-sized velum gesture initiated earlier

Longer post-Noral constriction

CN

Shorter Nmurmur

V N C

More extensive V nasalization

V

This pattern is precisely what we find in voiceless (relative to voiced) contexts in English.

Variation in temporal alignment: effects of voicing

English

Stimuli: /CEnC/ words where coda C = /s t d z/

(e.g., bent, bend, sent, send, sense, dense, dens). Speakers: 5 native speakers of American English.

Acoustic measures: N duration, post-N oral closure duration, and duration of V nasalization.

In measuring V nasalization, FFT spectra were inspected in 10 ms increments across the V. Nasalization onset = first spectrum with an identifiable low-frequency FN and/or a broadening of F1 BW and lowering of F1 amplitude.

Measuring V Nasalization

(a) (c)

(d) (e) (f)

(b)

Rel

ativ

e A

mp

litu

de

Frequency (in Hz)

0 1800 0 1800 0 1800

0 1800 0 1800 0 1800

0

40

80

120

0 40 80 120 160 200

Nasal Consonant Duration (ms)

Duration of Vowel Nasalization (ms)

N Duration (ms)

V D

urat

ion

(ms)

~Variation in temporal alignment: effects of voicing

AMERICANENGLISH

Scatterplot of VNCvoiceless (filled) and VNCvoiced (unfilled) tokens from 5 speakers.

Data show inverse relation between N and V durations.(R2 statistics for trend lines range from .27 to .45.)


R2 =

0

20

40

60

80

100

120

140

0 10 20 30 40 50 60 70 80

N Duration (ms)

C Closure Duration (ms)R2 =

0

20

40

60

80

100

120

140

0 10 20 30 40 50 60 70

N Duration (ms)

C Closure Duration (ms)Speaker 1 Speaker 2

Voi

cele

ss P

ost-

N C

losu

re (

ms)


V



CN

Shorter Nmurmur

Later onset of the velum gesture in voiced contexts is likely due to aerodynamic factors, with nasal leakage before full velum closure and the continued raising of the velum after closure (which expands the oral cavity) facilitating voicing (Hayes & Stivers, 2000; Solé, 2007).

Ikalanga

VNC: As in other Bantu languages, NC sequences are traditionally analyzed as prenasalized NC (Mathangwane, 1999). Most NCs in Ikalanga are voiced, although NC[voiceless] occur in borrowed–including some common–words.

Stimuli: Extensive word list with voiced VNCV (e.g., [danda]) and voiceless VNCV (e.g., [kenta]) sequences

Speakers: 6 native speakers of Botswanan Ikalanga


However, not all languages exhibit N shortening in pre-voiceless contexts. Our prediction is that these languages should also not show more extensive vowel nasalization in these contexts.


Duration of oral and nasalized V, N, and C in VNCV sequences.

IKALANGA

~No significant effect of voicing on duration of N or coarticulatory nasalization; total duration of nasalization (V and N) is constant across contexts.

Duration (ms)

0 100 200 300 400

VNCV voiceless

VNCV voiced

Duration (ms)

V oral

V nasal

N

C

≈

Variation in temporal alignment: effects of vowel length

A second context known to give rise to variation in N duration is length of a preceding V.

Short V + Long N

Shorter oral constriction

Long V + Short N

V N

Oral closure

Vowel

V N

Same-sized velum gesture

Loweredvelum



Thai (Onsuwan, 2005)

Stimuli: Extensive set of CVN and CV:N words produced by 4 speakers

American English

Stimuli: CVN words with (long) tense and (short) lax Vs (e.g., seen, sin, pain, pen) produced by 6 speakers

This pattern is upheld by data from Thai and English.

0 100 200 300 400

English laxVN

English tenseVN

Thai VN

Thai V:N

Duration (ms)

V oral

V nasal

N


Duration of N and oral and nasalized V in Thai and English CVN sequences. (Thai data from Onsuwan, 2005)

The longer N is, the less extensive is the anticipatory nasalization on V.


VoicingVNT (shorter N, greater V NAS) vs. VND: English (our lab; Cohn)

Vowel lengthV:N (shorter N, greater V NAS) vs. VN: English, Thai (our lab)

FricationVNS (shorter N, greater V NAS) vs. VNT: Italian (Busà 2007) Japanese (Hattori et al. 1958)

The inverse relation between duration of N and duration of V nasalization is found for other contexts and in other languages as well:

Production summary:

Coarticulatory vowel nasalization shows considerable temporal variation across contexts, yet nasal gestures in codas have temporal stability: contexts with shorter N—including contexts that would appear to induce N shortening for substantially different phonetic reasons—have more anticipatory vowel nasalization.

Variation in temporal alignment:Perceptual equivalence between V and N

~

In view of the co-variation in production between V and N, for the past few years we have tested the perceptual hypothesis that listeners are more sensitive to total nasalization in the rhyme than to the precise alignment of oral and nasal gestures.

~

~Our method uses a variant of the trading relations paradigm in which we orthogonally vary duration of N and temporal extent of V nasalization. We have tested this approach with speakers of different languages, and with various types of stimuli, and I report here one set of findings.Stimuli: original [gaba] and [gamba]

Using cross-splicing techniques, we co-varied N duration with duration of vowel nasalization, yielding:

(a) 9-step [b-mb] series which incrementally replaced portions of oral pulsing for the stop with nasal murmur

(b) 2 degrees of vowel nasalization: slight (20%) and heavier (52%)

~

should be hardest for listeners

should be easiest for listeners

If heard as perceptually equivalent, then:

Listeners: 28 American English speakers

Perceptual equivalence between V and N ~

Stimuli were paired in 3 types of discrimination pairings to determine whether listeners treat nasality on V and N as perceptually equivalent.

N-only pairs: shorter Ns paired with longer Ns(V NAS held constant)

"Different nasality" pairs:slight V NAS + short N durationpaired with heavier V NAS + long N duration

"Similar nasality" pairs:slight V NAS + long N durationpaired with heavier V NAS + short N duration

~

Different nasality pair gaSmSba - gaLmLba

Similar nasality pair gaLmSba - gaSmLba

Time (s)0 1.151

0

7500

Time (s)0 1.13208

0

7500


~g a a m b a

g a a m b a

~

g a a m b a

~

g a am b a

~

/gaba/ - /gamba/

0

20

40

60

80

Different Nasality N-Only Similar Nasality

Percent Correct

Pooled responses of 28 listeners

~

Prediction: Different Nasality > N-only > Similar Nasality (Slight VNAS + short N

(Heavy VNAS + short N paired with heavier V NAS

paired with Slight VNAS + short N) + long

N)


Prediction: Different Nasality > N-only > Similar Nasality


/gaba-gamba/

0

25

50

75

100

1,5 2,6 3,7 4,8 5,9

N Duration

Percent Correct

N-only

DifferentNasalitySimilarNasality

~

Production and perception summary

Summary

• Nasal gestures in codas have temporal stability: contexts with shorter N have more anticipatory vowel nasalization.

• The perceptual counterpart to (relative) temporal stability of nasalization is that listeners are sensitive to total nasalization across the syllable rhyme, responding to vocalic and consonantal nasality as though perceptually equivalent.

Phonological implications

The phonetic findings are consistent with widely attested phonological patterns:

• Phonologically, nasal codas are robust. Some languages allow only nasals as codas, and languages that have lost coda consonants and for which we have a detailed chronology (e.g., Romance, Chinese; Chen & Wang, 1975) show that N loss follows a slower trajectory than does oral stop loss.

This robustness is in keeping with temporal stability of the nasal gesture in the syllable rhyme.

~


~

~

• At the same time, the tight link between N and coarticulatory V nasalization in production and perception should mean that N and V are closely related in phonology, as found, for example, in the historical change VN > V.

The phonological evolution of this change is influenced by the same factors that trigger the phonetic co-variation reported here: voiceless obstruents, fricatives, preceding long vowels

(Hajek, 1997; Sampson, 1999) are also contexts that are especially likely to lead to phonological VN > V.

~


VN VN V V V V V V V

VN VN VN VN V V V (VN) (VN)

Data from Hajek for 9 Northern Italian dialects

• At the same time, the tight link between N and coarticulatory V nasalization in production and perception should mean that N and V are closely related in phonology, as found, for example, in the historical change VN > V.

The phonological evolution of this change is influenced by the same factors that trigger the phonetic co-variation reported here: voiceless obstruents, fricatives, preceding long vowels

(Hajek, 1997; Sampson, 1999) are also contexts that are especially likely to lead to phonological VN > V.

~

~

~

Dialect 1 2 3 4 5 6 7 8 9

VNT

VND

~

~

~

~

~

~

~ ~

~

~


There is evidence of this proposed "later stage" in additional experiments that we have conducted with bet-bent stimuli. (Recall that English N is often extremely short in a pre-voiceless context, and especially short before [t].)

It's tempting to speculate that co-variation/equivalence may be a phonetic pre-condition to such changes. At a later stage, listener insensitivity to the precise segmental alignment of the target property may lead to a point at which the original source—which is only variably present in the input—is no longer informative.

I hypothesize that co-variation in production and equivalence in perception between coarticulatory source (N) and effect (V) serve as a phonetic path to sound changes in which the coarticulatory source is lost over time but its coarticulatory effects remain.

~

Additional perceptual testing

The approach was identical to that for /gaba/-gamba/:

V nasalization and N duration (0-85 ms in 9 steps) were orthogonally varied and the stimuli were paired in 3 types of discrimination pairings.

N-only pairs

"Different nasality" pairs

"Similar nasality" pairs

We speculated that, because of the extreme shortness of N in this context in natural productions, listeners might be especially sensitive to vowel nasalization in these pairs. If so, then Different and Similar Nasality bet-bent pairs might be discriminated equally well—and better discriminated than N-only pairs.

/bEt - bE)nt/


0

20

40

60

80

Percent Correct

Different Nasality

N-Only

Similar Nasality

/bEt - bE)nt/

As expected, listeners attended more to vowel nasalization than to total nasalization across the syllable rhyme in the Similar Nasality pairings (the Similar Nas —Different Nas difference was not significant).

However, this outcome is not representative of the responses of all listeners.

0

20

40

60

80

100

6 listeners 16 listeners

Percent Correct

Different Nasality N-Only Similar Nasality


/bEt - bE)nt/

"Perceptual equivalence" pattern (as for /gaba-gamba/)

V NAS dominant pattern

Listener 2 bet-bent

0

20

40

60

80

100

1 2 3 4 5 6 7 8 9 10

Stimulus Number

% Reported bent

Listener 1 bet-bent

0

20

40

60

80

100

1 2 3 4 5 6 7 8 9 10

Stimulus Number

% Reported bent

N Duration (stimulus number)

N Duration (stimulus number)

Additional perceptual testing: /bEt - bE)nt/

V0

V33

V66

%V NAS

"Perceptual equivalence" listener

Parallel differences are seen in the identification data for these listeners.

"V dominant" listener


Taking together the findings for /gaba-gamba/ and /bt-bnt/, we find—as expected—that (some) listeners are more sensitive to vowel nasalization in contexts that trigger especially short N and extensive coarticulatory nasalization.

Moreover, we find that not all listeners arrive at the same generalization about what constitutes a distinction between VC and VNC. Some listeners are more sensitive to differences in total nasalization while others are particularly sensitive to differences in V nasalization.

~ ~

Such an account of phonologization differs from the often-cited view of the listener as misperceiving a speaker's intended signal (Ohala, 1981, 1993; Blevins, 2007).

Regarding phonologization of coarticulation (here, VN > V), we suggest that listener insensitivity to the precise segmental timing of the target property (nasalization) can—and does—lead to a point at which the original source (N) is less informative than the coarticulatory effect (V).

~

~

Conclusion

Ohala: listeners factor out the acoustic "distortion" due to coarticulation, as long as they detect the source of the distortion:

Speaker Listener

/n/ /n/

distorted by vocal tract into reconstructed as

[E)n] heard as [E)n] because of

knowledge of coarticulatory effects of nasals

Conclusion

Ohala: But if the source of the "distortion" goes undetected, the coarticulatory effects will not be parsed properly:

Speaker Listener

/n/ /E)/

distorted by vocal tract into reconstructed as

[E)(n)] heard as [E)] [E)]

later produced

as

In the current approach: the perceptual consequence of co-variation in production is that listeners formulate equivalence classes based on the (lawfully) variable input signal (e.g., [n], [n], []) and they arrive at generalizations (e.g., presence vs. absence of nasality in the syllable rhyme) fully consistent with the input.

~ ~~

If copied by other speakers, this misperception could become a systematic change in a language.

Conclusion

Production: Data from different languages and for different phonetic contexts show that, in tautosyllabic VN sequences, duration of coarticulatory

V nasalization and duration of N co-vary, such that velum lowering in the syllable rhyme is relatively stable across phonetic contexts.

Phonology: Co-variation in production and equivalence in perception between coarticulatory source and effects may be phonetic precursors to the coarticulatory effect becoming a distinctive property in a

language.

Perception: Listeners treat N and V as perceptually equivalent and are more sensitive to total nasalization in the rhyme than to the precise

alignment of oral and nasal gestures, although in contexts in which N is often absent in production, listeners attend more to V.

~

~

ReferencesBusà, M. G. (2007) Coarticulatory nasalization and phonological developments, in M. J. Solé, P. S. Beddor, and M. Ohala (eds.), Experimental Approaches to Phonology, pp. 155-174. Oxford: OUP.

Blevins, J. (2007) Interpreting misperception, in M. J. Solé, P. S. Beddor, and M. Ohala (eds.), 144-154.

Chen, M. Y., Wang, W. S-Y. (1975) Sound change: actuation and implementation. Language 51, 255-281.

Cohn, A. (1990) Phonetic and phonological rules of nasalization. UCLA WPP 76, 1-224.

Hajek, J. (1997) Universals of Sound Change in Nasalization. Boston, MA: Blackwell.

Krakow, R. A. (1993) Nonsegmental influences on velum movement patterns: syllables, sentences, stress, and speaking rate. In M. K. Huffman and R. A. Krakow (eds.), Nasals, Nasalization, and the Velum, pp. 87-113. New York: Academic Press.

Malécot, A. (1960) Vowel nasality as a distinctive feature in American English. Language 36, 222-229.

Ohala, J. J. and Busà, M. G. (1995) Nasal loss before voiceless fricatives: a perceptually-based sound change. Rivista di Linguistica 7, 125-144.

Mathangwane, J. T. (1999) Ikalanga Phonetics and Phonology: A Synchronic and Diachronic Study. Stanford, CA: CSLI Publications.

Onsuwan, C. (2005) Temporal relations between consonants and vowels in Thai syllables. University of Michigan doctoral dissertation.

Sampson, R. (1999) Nasal Vowel Evolution in Romance. Oxford: OUP.

Solé, M.-J. (1995) Spatio-temporal patterns of velopharyngeal action in phonetic and phonological nasalization. Language and Speech 38, 1-23.

Solé, M.-J. (2007) Compatibility of features and phonetic content: the case of nasalization, in Proceedings of the 16th International Congress of Phonetic Sciences, Saarbrücken, Germany.

Vaissière, J. (1988) Prediction of velum movement from phonological specifications. Phonetica 45, 46-63.

Whalen, D. H., Beddor, P. S. (1989) Connections between nasality and vowel duration and height: elucidation of the Eastern Algonquian intrusive nasal. Language 65, 457-486.

Prediction: Different Nasality > N-only > Similar Nasality (Slight VNAS + short N

(Heavy VNAS + short N paired with heavier V NAS

paired with Slight VNAS + short N) + long

N)


0

20

40

60

80

English Ikalanga

Percent Correct

VSNS-VLNLNasal onlyVLNS-VSNL

VSNS-VLNL

~ ~

N only

VLNS-VSNL

~ ~

English Ikalanga

Both groups of listeners showed the predicted pattern although, not surprisingly, English listeners had greater difficulty discriminating stimuli with similar nasality.

Time (s)1.76593 2.07034

–0.2011

0.2169

0

Time (s)1.76773 2.06528

–0.2011

0.2169

0


V


Oral closure

Vowel Loweredvelum



CN

Shorter Nmurmur

V N C

Documents

The Phonetics and Phonology of Nasal Gestures Patrice Speeter Beddor University of Michigan Supported by NSF