Acoustic Cues to Laryngeal Contrasts in Hindi

Susan Jackson and Stephen Winters

University of Calgary

Acoustics Week in Canada

October 14, 20111

Introduction• Speakers are sensitive to the phonemic distinctions of their native language.

• These distinctions are perceived through acoustic cues in the input, which are also language-specific.

• For example, a syllable-initial voiceless stop =

• aspirated in English

• unaspirated in French

• Certain cues in the speech stream might have meaning for one listener group while being superfluous or disregarded by another (Abramson & Lisker, 1970).

Introduction• Jackson (2009): tested whether L1 English and L1 French listeners would perceive Hindi’s four-way system of laryngeal contrasts differently.

• Hindi laryngeal contrasts:

• two main elements: voicing and aspiration

• Together, these create a 2x2 paradigm of four distinct phonemes:

• voiced unaspirated e.g. /b/• voiceless unaspirated e.g. /p/• voiceless aspirated e.g. /ph/• voiced aspirated e.g. /bɦ/

Voiced Aspirated Stops• Hindi’s voiced aspirated stops are somewhat unique--

• They involve the production of four acoustic cues in sequence:

1. Voicing during the closure phase of the stop

2. A release burst following the stop closure

3. Periodic breathy voicing mixed in with turbulent aspiration noise

4. A steady vowel portion, produced in modal voice

An example

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/bɦa.ˈvɪʃ.ja/ ‘future’

voiceasp

Initial Assumptions• Distinctive Feature-based predictions:

1. French stops are distinguished by the [voice] feature

• French listeners would be more sensitive to [voice] contrasts in Hindi.

• E.g., [b] ~ [p] or [bɦ] ~ [ph]

2. English stops are distinguished by the [spread glottis] feature

• English listeners would be more sensitive to [spread glottis] contrasts in Hindi.

• E.g., [p] ~ [ph] or [b] ~ [bɦ]

• Both groups should be sensitive to contrasts involving both features.

Earlier Findings, Part 1

• ABX discrimination task: generally confirmed these predictions.

Earlier Findings, Part 2

• Deviations from the predicted pattern generally involved the voiced aspirated stops.

New Directions• Note: voiced aspirated stops were novel to both listener groups yet employed both [voice] and [spread glottis] features.

• It’s necessary to go beyond the features and consider the phonetic cues involved• Goal:

• disambiguate the role of aspiration and (closure) voicing cues in the perception of Hindi laryngeal contrasts

• Strategy: • independently combine each acoustic cue in spliced stimuli to determine its effect on perception of those laryngeal contrasts by both native (Hindi) and non-native (English) listeners.

Introducing: The Cues1. Aspiration

• Presence

• Absence

2. Aspiration quality

• Voiceless

• Breathy voiced

3. Closure voicing duration

• Short (cues breathy voiced stops)

• Long (cues voiced stops) (Schieffer, 1992)

Raw Materials• 10 native Hindi (L2 English) speakers produced the raw tokens from which stimuli were created.

• They were recorded reading 178 Hindi nonce words which had stop, fricative and affricate onsets.

• Only stop-initial words were used in perception study.

• Two places of articulation: velar and retroflex.

• Two speakers: one male and one female.

• Length of closure voicing varied by place of articulation and speaker.

• average difference of 41 msec between voiced (=long) and breathy (=short) stops

Raw Materials• Two features with three values each...

Long closure voicing Voiceless aspirationShort closure voicing Breathy voiced aspirationNo closure voicing Unaspirated ... were combined to create a paradigm of 9 stimuli

LongCV-Asp ShortCV-Asp NoCV-Asp

LongCV-BreathyAsp ShortCV-BreathyAsp NoCV-BreathyAsp

LongCV-Unasp ShortCV-Unasp NoCV-Unasp

b:h bh ph

b:ɦ bɦ pɦ

b: b p

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‘LongCV-BreathyAsp’

Breathy voice + closure voicing

‘LongCV-Asp’

Aspiration (-voice) + closure voicing

‘LongCV-Unasp’

Unaspirated + closure voicing

Perception Experiment• ABX task:

• Listeners hear a pair of stimuli, A and B, followed by a token X

• Task: determine whether X matches A or B

• Inter-stimulus interval: 720 msec

• Listeners: students at the University of Calgary

• 15 native English speakers

• 15 native Hindi speakers

Perception Experiment:Nitty Gritty

• Each of the 9 stops was paired with 4 contrastive items.

• For example, [p] was paired with:

• [ph] and [pɦ] (= aspiration contrasts)

• [b] and [b:] ( = closure voicing contrasts)

• Each pair was presented in both orders

• Each pair was presented at two places of articulation

• Each pair was produced by two different speakers

• Total: 288 randomized trials

• Duration of experiment 25 minutes

Results: Aspiration contrasts

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English P-value

1-2 < .001

2-3 0.001

1-3 0.008

Hindi P-value

1-2 < .001

2-3 0.999

1-3 < .001

1 2 3

Results: Aspiration contrasts• No main effect of language of listener!

• However, a significant effect of contrast type

• English: Asp ~ Unasp > Breathy ~ Unasp > Asp ~ Breathy

• Hindi: Asp ~ Unasp, Breathy ~ Unasp > Asp ~ Breathy

• The Asp ~ Breathy contrast is difficult for both groups of listeners;

• But the English listeners are sensitive to the quality of aspiration.

• Basically: (phonetically) unfamiliar contrasts are more challenging.

Results: Closure Voicing contrasts

18

English P-value

1-2 0.024

2 -3 0.029

1-3 0.829

Hindi P-value

1-2 0.001

2 -3 0.003

1-3 0.733

1 2 3

• Native language of listener once again didn’t matter.

• But another significant effect of contrast type…

• English: LongCV ~ NoCV, ShortCV ~ NoCV > LongCV ~ ShortCV

• Hindi: LongCV ~ NoCV, ShortCV ~ NoCV > LongCV ~ ShortCV

• The presence vs. absence of closure voicing mattered to listeners;

• But the duration of closure voicing did not.

• However, there was a significant effect of closure voicing length on the perception of aspiration quality for both listener groups…

Results: Closure Voicing contrasts

Aspiration * voicing length (English)

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*

**

L N SL N SL N S

• pɦ ~ ph >

bɦ ~ bh, b:ɦ ~ b:h

• pɦ ~ p > b:ɦ ~ b:

• Apparent advantage in discrimination of breathy voiced aspiration when there is no closure voicing present.

Aspiration * voicing length (Hindi)

21

**

L N SL N SL N S

• pɦ ~ ph >

bɦ ~ bh, b:ɦ ~ b:h

• Same advantage in discrimination of breathy voiced aspiration when there is no closure voicing present.

Aspiration * voicing length: thoughts

• When closure voicing is present, it becomes more difficult to distinguish between breathy voiced aspiration and unvoiced aspiration.

• Without closure voicing, listeners may be forced to rely on cues in the aspirated portion of the stop

• that is, +/- concomitant vocal fold vibration.

• Aspiration quality may be perceptually integrated, somehow, with closure voicing.

Conclusions• Surprising similarity between both listener groups

• In particular: Hindi listeners don’t have an advantage in the perception of closure voicing contrasts.

• General trend: familiar contrasts are easier to process

• English listeners are somewhat sensitive to the distinction between voiceless aspiration and breathy voiced aspiration.

• Hindi listeners don’t display an advantage when this cue varies independently of closure voicing.

• Overall moral of the story: phonetics matters.

Merci!