The Role of F0 in the Perceived Accentedness of L2

Speech

Mary Grantham O’Brien

Stephen Winters

GLAC-15, Banff, Alberta

May 1, 2009

Thank you

• Roswita Dressler

• Annika Orich

• Valerie Haberl

• Robert MacDonald

• Silke Weber

• Andreas Berkefeld

Motivation• What effect does non-native prosody have on the

perceived accentedness and intelligibility of speech?

• Production studies: perceptual interference between L1 and L2 (Holm 2008; McAllister 1997).

• Possible to rate accentedness in unfamiliar foreign language (Major 2007)

• Perceptual studies: intelligibility, comprehensibility and accentedness (e.g., Munro et al. 2006; Kennedy & Trofimovich 2008)

Intelligibility of L2 speech

• “the extent to which a speaker’s utterance is actually understood” (Munro et al. 2006, p. 112)

• measured through listener transcriptions• Accented speech more intelligible if listeners

share L1 of speaker (Kennedy & Trofimovich 2008)

• Positively affected by intonation manipulation.

Role of intonation in perception of foreign accent

• Differs according to study and L1-L2 pairings• Segments• Duration

Cross-linguistic intonation

• Languages differ both in average pitch height and range of frequencies (e.g., Braun 1994; Ladd 1996)

• German vs. English intonation• Greater pitch range in English than in German

(Eckert & Laver 1994; Gibbon 1998; Mennen 2007)

• Bilingual intonation• Bilinguals adjust intonation, depending on

language being spoken (Mennen 2007)

The current study• Transplantation of both native and non-native intonation patterns onto the segments of the other language.

• German and English speakers

• Q1: Does mapping non-native intonation onto native segments affect perceived accentedness and intelligibility?

• Q2: Does mapping native intonation onto non-native segments affect perceived accentedness and intelligibility?

• Also: listeners included L2 German learners at a variety of proficiency levels.

Methodology: Stimuli• 24 German and English sentences

• 12 declarative

• 6 yes/no questions

• 6 WH-questions

• Produced by:

• L1 English/L2 German (female) speaker

• L1 German/L2 English (female) speaker

Stimulus Conversion• German speaker prosody transplanted onto English speaker segments,

• and vice versa…

• for productions in both languages.

• PSOLA-based manipulation algorithm developed by Mareüil & Vieru-Dimulescu (2006)

• Pink noise added to all stimuli for intelligibility test.

• 0 dB SNR for English stimuli

• +5 dB SNR for German stimuli

Stimuli Samples

• Unedited English:

• Converted English:

• Unedited German:

• Converted German:

Clear In Noise

Methodology: Tasks1. Intelligibility

• Listeners heard natural + converted sentences in noise

• Typed in answers to question “What did the speaker say?”

2. Accent rating

• Listeners heard natural + converted sentences in clear

• Rated accentedness on a scale from 0 to 6

• (0 = “no accent”, 6 = “most accent”)

• Two counterbalanced blocks: German and English

Methodology: Listeners• Subjects: 22 native listeners of Canadian English

• 14 males, 8 females

• Aged 20-25 (mean: 22 years)

• Beginning to advanced learners of German

• Levels A2-C1 on Common European Framework of Reference for Languages (mostly levels B1 and B2)

Results: AccentednessPerceived Accentedness

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

ef - natural ef - gF0 gf - natural gf - eF0

Stimulus Type

Accent Rating (0-6)

English German

Figure 3

Results: IntelligibilityIntelligibility

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

ef - natural ef - gF0 gf - natural gf - eF0

Stimulus Type

% Words Correctly Identified

English German

Figure 4

Results: German Accent Ratings by Listener Group

German Accent Ratings, by Listener Group

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

ef - natural ef - gF0 gf - natural gf - eF0

Stimulus Type

Accent Rating (0-6)

High Proficiency Low ProficiencyFigure 5

Results: German Intelligibility by Listener Group

German Intelligibility, by Listener Group

0%

10%

20%

30%

40%

50%

60%

ef - natural ef - gF0 gf - natural gf - eF0

Stimulus Type

% Words Correctly Identified

High Proficiency Low ProficiencyFigure 6

Results: Summary• Accentedness:

1. F0 transplantation decreases perceived accentedness of natively produced sentences…

2. But does not improve perceived accentedness of non-natively produced sentences.

• Intelligibility:

1. English sentences more intelligible than German

2. English speaker more intelligible than German in both language conditions

3. F0 manipulation reduces intelligibility in all conditions

Results: Summary• Low proficiency German learners based accent ratings more on prosodic features;

• High proficiency learners’ ratings based more on natural vs. manipulated.

• More top-down processing in case of high proficiency learners?

Conclusions• Prosodic characteristics do play a role in the perception of accentedness (or lack thereof).

• true for both L1 and L2 perception.

• L2 listeners better understood L2 speaker in adverse listening conditions.

• Note: “Interlanguage speech intelligibility benefit” (Bent & Bradlow, 2003)

• Note: PSOLA-based manipulation induced unnaturalness into speech stimuli.

• possible limitations of synthesis algorithm

Future research• Possible control: compare manipulated sentences with manipulated sentences.

• Also: perception of naturally produced F0 contours in both conditions (by phonetically trained speaker)

• Other directions: test native listeners of German

• Test broader range of speakers

• Test speakers of other languages with clearer prosodic differences

• Pitch Accent languages (French, Japanese)

• Tone languages (Chinese)

Accent Rating Screen

Results: NaturalnessPerceived Naturalness

0

0.5

1

1.5

2

2.5

3

3.5

4

ef - natural ef - gF0 gf - natural gf - eF0

Stimulus Type

Naturalness Rating (0-6)

English German