Intent vs. Surface: Recovering Acoustic Realization from Modern ASR for Pronunciation Training
Paper · 2026 · Seongjin Park
Summary
Computer-assisted pronunciation training usually compares an ASR transcript with the prompt the learner read. Modern recognizers, however, rely on language-model priors. They tend to output the word the speaker meant rather than the sounds actually produced, which hides learner errors. The author calls this "intent bias" and measures it across eight ASR systems from three architecture families on two L2 English corpora, L2-ARCTIC and speechocean762. Systems with lower WER turn out to conceal more mispronunciations.
As a remedy, the paper proposes surface-faithful reranking. An LM-free phoneme recognizer supplies a reference phone string, and each N-best hypothesis is converted to phonemes with g2p-en. The candidate closest under a PanPhon articulatory-feature edit distance is then used for word-level error detection, while the ordinary top-1 transcript is still shown to the learner. The method needs no retraining and no access to model internals. It cuts false acceptance of mispronunciations by about six points, with consistent gains across age groups and L1s. The work shows that WER alone is a poor criterion for choosing ASR in educational tools.
Key points
- Overcorrection is systematic. Across autoregressive, hybrid CTC-RNNT and CTC-only systems, lower WER correlates with higher overcorrection. With Parakeet, 82.0% of speechocean762 utterances contain at least one masked mispronunciation in the top hypothesis.
- Setup: the main systems are NVIDIA Parakeet (FastConformer, hybrid CTC-RNNT) and Whisper large-v2 via faster-whisper, each with K=10 hypotheses. Phoneme distance uses 24-dimensional PanPhon feature vectors with Hamming-based substitution costs, and no weights are tuned.
- False acceptance rate (FAR) on severe errors drops from 80.8% to 74.8% on L2-ARCTIC (six L1s, 24 speakers). On the speechocean762 test split (n=2,497), FAR drops from 70.6% to 65.0%. The cost is a false rejection rate rise of 1.7–3.0pp, mostly on short function words.
- The gains are capped by the content of the N-best list. The K=10 oracle FAR is still 56.9%, and widening Whisper's beam to K=20 adds only 1.4pp. The phoneme recognizer itself has a 19.2% error rate on L2-ARCTIC.
- To complement WER, the author introduces a new metric called Pronunciation Preservation Rate, defined as PPR = 1 − FAR. On the speechocean762 test split it ranges from 25.8% to 59.0%. Future work includes pronunciation-aware decoding and multi-pronunciation lattices.
Fields, topics and concepts
📚 Shelves 7The field of science this work belongs to (OpenAlex fields).Computer Science · 18,614 worksArtificial Intelligence · 17,965 worksArts and Humanities · 17,450 worksLanguage and Linguistics · 17,296 worksPsychology · 1,649 worksExperimental and Cognitive Psychology · 930 worksSignal Processing · 493 works
🧭 Topics 1Research subjects and languages the work is about.Speech & spoken language · 519 works
Cite
Cite as Seongjin Park. 2026. Intent vs. Surface: Recovering Acoustic Realization from Modern ASR for Pronunciation Training. Proceedings of the 21st Workshop on Innovative Use of NLP for Building Educational Applications (BEA 2026).
@inproceedings{park2026intent,
title = {{Intent vs. Surface: Recovering Acoustic Realization from Modern ASR for Pronunciation Training}},
author = {Seongjin Park},
booktitle = {Proceedings of the 21st Workshop on Innovative Use of NLP for Building Educational Applications (BEA 2026)},
year = {2026},
doi = {10.18653/v1/2026.bea-1.23},
url = {https://doi.org/10.18653/v1/2026.bea-1.23}
}References
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