Present Experiment

Introduction

Coarticulatory Timing and Lexical Effects on Vowel Nasalization in English: an Aerodynamic Study

Jason BishopUniversity of California, Los Angeles

In English, vowels show significant nasalization when preceding a nasal consonant. The extent of this coarticulation, however, depends on other aspects of the phonetic context. For example, in (C)VNC sequences, nasalization is more extensive when:

initial C is an aspirated stop, or if NC are tautosyllabic (Cohn 1995). V is stressed (Krakow 1993). C is voiceless rather than voiced (Malécot 1960).

Beddor (2007) suggests the difference between a voiced C context (VND) and voiceless C context (VNT) is not due to more nasalization as such, but to the earlier onset of velum lowering when the oral articulation for N is shorter:

Constant-sized velum-lowering gesture begins later when N is longer, overlapping less with vowel

Constant-sized velum-lowering gesture begins earlier when N is shorter, overlapping more extensively with vowel

Less Nasalization

More Nasalization

Beddor (2007) presents acoustic evidence from VNC productions of 5 speakers of American English that this trading relationship between the durations of nasal consonants (N) and the duration of coarticulatory vowel nasalization (Ṽ), holds (R2 ranging from .27 to .45).

Goals 1.) Corroborate the findings in Beddor 2007 with aerodynamic data. 2.) Examine possible lexical effects as an additional source of variation in extent of coarticulatory vowel nasalization.

Methods 4 speakers of American English (2 male, 2 female; ages 21 – 28) Speakers read (C)VNC tokens embedded in the carrier sentence “Please say ______ with me”. Oral and nasal airflow collected simultaneously with audio recordings.

Variables

Duration of the nasal consonant (N) Duration of significant nasal airflow over the vowel (Ṽ) (i.e., nasal flow above the levels present in non-nasal context controls –e.g., sped for spend) Proportion of the vowel with significant nasal airflow (duration of significant nasal airflow over the vowel / total duration of vowel)

Vowel Nasalization and Nasal Consonant Duration: VNT and VND Contexts

0

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300

0 20 40 60 80 100 120 140 160 180

Duration N (ms)

Dura

tion Ṽ

(m

s)

Results: Across Voicing Context

Figure 2. Scatterplot showing vowel nasalization as a function of the duration of the nasal consonant for (C)VNC test words (across voicing contexts for C). Although the trend is in the direction of an inverse relationship, the duration of N accounts for very little of the variation in Ṽ. R2 = .03(Speaker 1), .05(Speaker 2), .02(Speaker 3), .05(Speaker 4).

1. Evidence for an inverse relationship not found across voicing contexts:

2. N duration is a better predictor of Ṽ duration within voicing contexts:

VNT

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0 20 40 60 80 100 120 140 160

Duration N (ms)

Dur

atio

n Ṽ

(ms)

VND

0

100

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300

0 20 40 60 80 100 120 140 160 180

Duration N (ms)

Dur

atio

n Ṽ

(ms)

Figure 3. Vowel nasalization and nasal consonant duration in a voiceless obstruent context. R2 for trend lines = .61(Speaker 1), .16(Speaker 2), .25(Speaker 3), .10(Speaker 4).

Figure 4. Vowel nasalization and nasal consonant duration in a voiced obstruent context. R2 for trend lines = .29(Speaker 1), .28(Speaker 2) .23(Speaker 3), .37(Speaker 4).

Speaker 1High Frequency

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0 20 40 60 80 100 120 140

Duration N (ms)

Dura

tion

? (m

s)

Speaker 1Low Frequency

R2 = 0.23

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0 20 40 60 80 100 120 140

Duration N (ms)

Dur

atio

n ?

(ms)

Speaker 2High Frequency

R2 = 0.12

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Duration N (ms)

Dura

tion

? (m

s)

Speaker 2Low Frequency

R2 = 0.19

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0 25 50 75 100 125 150Duration N (ms)

Dura

tion

Ṽ (m

s)

Speaker 3High Frequency

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0 25 50 75 100 125

Duration N (ms)

Dura

tion

Ṽ (m

s)

Speaker 3Low Frequency

R2 = 0.15

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0 25 50 75 100 125

Duration N (ms)

Dur

atio

n Ṽ (

ms )

Lexical Effects: Neighborhoods

Lexical Effects: Frequency

Summary Within both the voiced and voiceless context, the duration of N accounted for considerable amounts of the variation in Ṽ; not true when voicing contexts were considerable together. This differs from what is reported in Beddor 2007, where the strongest relationship was found across

voicing contexts.

Scarborough (2004) measured anticipatory nasal coarticulation in two lexical confusability conditions, finding more extensively nasalized vowels in more confusable or, here, lexically “difficult” words:

Easy (or high R : high frequency within sparse phonological neighborhoods)

Difficult (or low R : low frequency within dense phonological neighborhoods)

Three Questions

1.) Does lexical frequency (independent of neighborhood size/lexical difficulty) influence the relation between N and Ṽ ?

2.) Does neighborhood size correlate with degree of nasalization ?

3.) How does lexical difficulty influence the relation between N and Ṽ ?

Subsets of the production data with the relevant lexical properties were examined to address these questions. Lexical statistics were taken from the Washington University Speech and Hearing Lab Neighborhood Database.

Speaker 1

R2 = 0.49

0.4

0.6

0.8

1

0 5 10 15 20

# of Neighbors

Prop

ortio

n V

Nas

aliz

ed

Speaker 4

R2 = 0.36

0.2

0.4

0.6

0.8

1

0 5 10 15 20# of Neighbors

Prop

ortio

n V

Nasa

lized

Speaker 2

R2 = 0.15

0.2

0.4

0.6

0.8

1

0 5 10 15 20

# of Neighbors

Prop

ortio

n V N

asal

ized

Speaker 3

R2 = 0.15

0.2

0.4

0.6

0.8

1

0 5 10 15 20

# of Neighbors

Prop

ortio

n V N

asal

ized

Word# of

Neighbors

spent 3

spend 5

grant 6

want 9

ant 12

tint 14

lent 17

cant 18

went 19

Speaker 1Difficult

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0 20 40 60 80 100 120

Duration N (ms)

Dura

tion Ṽ (

ms)

Speaker 2Difficult

R2 = 0.33

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150

200

0 25 50 75 100 125

Duration N (ms)

Dura

tion

Ṽ (

ms)

Speaker 3Difficult

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0 25 50 75 100 125

Duration N (ms)

Dura

tion Ṽ

(m

s)

Speaker 1Easy

R2 = 0.34

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250

0 20 40 60 80 100 120 140

Duration N (ms)

Dura

tion Ṽ (m

s)

Speaker 2Easy

R2 = 0.37

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Duration N (ms)

Dura

tion Ṽ

(m

s)

Speaker 3Easy

R2 = 0.11

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0 25 50 75 100 125 150 175

Duration N (ms)

Dura

tion Ṽ (m

s)

Speaker 4Easy

R2 = 0.3459

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Duration N (ms)

Dura

tion Ṽ

(m

s)

Speaker 4Difficult

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Duration N (ms)

Dura

tion Ṽ

(m

s)High Frequency Low Frequency

Easy Difficult

Word log freq# of

Neighbr R

rent 2.3222 17 0.066844

lend 2.1461 17 0.058803

bent 2.5315 17 0.061989

June 2.9685 16 0.090507

can't 3.2304 18 0.086955

bend 2.3802 18 0.057645

went 3.705 19 0.16318

and 5.4602 12 0.140092

MEAN3.09301

3 16.75 0.09

High Frequency

Word log freq# of

Neighbr R

dent 1.301 19 0.033844

lent 1.699 17 0.041772

rend 1 19 0.025448

scant 1.699 3 0.209611

wand 1 9 0.053691

canned 1.7782 16 0.041803

gent 1 17 0.027906

wend 1 18 0.028739

MEAN 1.30965 14.75 0.058

Low Frequency

Results: Within VNT and VND

Word log freq

# of Neighbr R

want 3.5198 9 0.199035

grand 2.6812 7 0.166447

scant 1.699 3 0.209611

spend 2.7243 5 0.216822

grant 2.6721 6 0.240051

spent 3.017 3 0.294879

MEAN 2.7189 5.5

0.221141

Easy

Wordlog

freq# of

Neighbr R

bent 2.5315 170.0619888

3

rent 2.3222 170.0668439

8

dent 1.301 190.0338437

2

lent 1.699 170.0417721

8

canned 1.7782 16

0.04180287

bend 2.3802 180.0576446

6

MEAN2.00201

7 17.333330.0506493

8

Difficult

1. N and Ṽ: trend towards inverse correlation for high frequency, positive

correlation for low frequency tokens

2. Neighborhood size and vowel nasalization positively correlated (R2 = .15 – .49)

3. N and Ṽ: inversely correlated for lexically easy words, unrelated or positively

correlated for lexically difficult tokens

Figure 5. Vowel nasalization and nasal consonant duration for high and low frequency subsets of the tokens (three repetitions of 8 tokens plotted for each frequency condition).

Speaker 4High Frequency

R2 = 0.1953

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Duration N (ms)

Dura

tion

Ṽ (m

s)

Speaker 4 Low Frequency

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Duration N (ms)

Dur

atio

n Ṽ

(m

s)

Figure 6. Proportion vowel nasalized (Ṽ/Vtotal) and neighborhood size (each point represents average values over three repetitions of each of nine tokens).

Figure 7. Vowel nasalization and nasal consonant duration for lexically easy and difficult words (high and low R, respectively). Three repetitions of 6 tokens plotted for each lexical type).

Word List

Word List

Word List

Conclusion

ReferencesBeddor, P. (2007). Nasals and nasalization: the relation between segmental and coarticulatory timing. Proceedings of the 16th International Congress of Phonetic Sciences, 249-254.

Cohn, A. (1990). Phonetic and phonological rules of nasalization. UCLA Working Papers in Phonetics 76, 1 – 224.

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

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

Tatham, M. & Morton, K. (2006). Speech production and perception. New York: Palgrave.

The results presented here are in general agreement with those in Scarborough 2004:

Speakers produced more, not less, coarticulation for tokens from denser phonological neighborhoods.

Further, they have implications for patterns of gestural alignment discussed in Beddor 2007: A tendency to decrease vowel nasalization in the presence of a longer nasal consonant, as predicted by Beddor, is apparent in the productions of these 4 speakers.

But: this effect is restricted to just those lexical conditions expected to be easy for listeners: high-frequency words and words of a high frequency within sparse neighborhoods.

Such findings are highly suggestive of what we should expect in a more listener-oriented communication task (more coarticulation for low frequency/difficult words regardless of the duration of the nasal consonant), and as such are very difficult to understand under a view of coarticulation as reduction (e.g., Thatham & Morton 2006).

Figure 1. From top to bottom channels: Audio, oral airflow, nasal airflow for the sentence “Please say bend with me.” Black dotted line shows duration of the vowel with significant nasal flow; red dash dot line shows the duration of the nasal consonant. Zero nasal flow is referenced to nasal flow during the vowel of non-nasal [bɛt].

500 ml/s

1000 ml/s