English stress system :: Difficulties for learners

• position of stress, strength of stress contrasts & manner of production
• acoustic realizations of stress contrasts under inspection here
• reduction of unstressed vowels in terms of shrinking the vowel space area (VSA) and relative shortening

The L1 effect

Why we do this?

Continuation of a previous study: acoustic syllable prominence estimates as prosodic proficiency predictors (Kallio et al. 2022)

• vowel quality disregarded

→ a pilot study to investigate the reduction of unstressed vowels in terms of centralization & relative duration

RQs

1. Does the degree of VSA shrinkage differ between English speaker groups with respect to their L1?

2. Does the degree of vowel shortening differ between English speaker groups with respect to their L1?

• EFL groups expected to differ from native speakers in both features related to vowel reduction

• Differences expected between EFL groups, e.g. in terms of vowel shortening

Speech data

• 16 speakers; 4 speakers from 4 L1s: English (Br), Hungarian, Polish, Slovak
• L2 speakers at B1 level proficiency
• Each read a narrative text consisting of 16 sentences (productions ~1.5 min)
• Read speech → more or less comparable productions of vowels in same contexts

Data preparation

• Vowel segments annotated using a forced aligner, onsets & offsets corrected manually in Praat

• Binary stress annotation based on standard British English transcription of the narrative text (weak forms ignored, e.g. that always transcribed ðæt not ðət)

• Nasalized vowels & vowels in context with rhotics and approximants excluded

• Number of vowels selected for analysis per speaker:

  Stressed: 448 – 567

  Unstressed: 686 – 819

Analysis

• Formant measurements extracted at 7 time points in vowel intervals with a Praat script
• Midpoint measures of F1 & F2 used here to determine VSAs
• densityarea (Fruehwald 2023); density polygons for 0.8 probabilities
• Formant measurements normalized using the Nearey method (vowel-extrinsic)
• Comparison of VSAs & relative duration differences of stressed & unstressed vowel productions

Results: VSAs

Degree of VSA shrinkage

vowel_area ~ stress * l1

Degree of vowel shortening

log10(duration) ~ stress * l1

Discussion

✔️ Yes, we have differences in the VSAs

• degree of VSA shrinkage larger for L1 than L2 speakers
• differences between L2 groups: shrinkage largest for Hungarian and smallest for Slovaks
• also differences in the size of stressed VSAs

→ effect of L1-specific vowel system?

• inter-speaker variation evident

Discussion

✔️ Yes, we have differences in reducing vowel durations

• all L2 speakers differ from natives

→ insufficient reduction of unstressed vowels or misplacement of word stress?

• average vowel shortening notably smaller for Hungarian EFL speakers than for the others

→ possible effect of quantity system?

Next steps

• More speakers per group to analyze
• How about other L1s such as Finnish/Estonian EFL speakers?
• Looking at vowel categories separately
• Including dynamic formant movements

Thank you!

Audio samples

“Instead, we were very surprised to see lots of different types of vegetables.”