Linguistically Informed Evaluation of Multilingual ASR for African Languages

Fei-Yueh Chen, Lateef Adeleke, C. M. Downey


Abstract
Word Error Rate (WER) mischaracterizes ASR models’ performance for African languages by combining phonological, tone, and other linguistic errors into a single lexical error. By contrast, Feature Error Rate (FER) has recently attracted attention as a viable metric that reveals linguistically meaningful errors in models’ performance. In this paper, we evaluate three speech encoders on two African languages by complementing WER with CER, and FER, and add a tone-aware extension (TER). We show that by computing errors on phonological features, FER and TER reveal linguistically-salient error patterns even when word-level accuracy remains low. Our results reveal that models perform better on segmental features, while tones (especially mid and downstep) remain the most challenging features. Results on Yoruba show a striking differential in metrics, with WER=0.788, CER=0.305, and FER=0.151. Similarly for Uneme (an endangered language absent from pretraining data) a model with near-total WER and 0.461 CER achieves the relatively low FER of 0.267. This indicates model error is often attributable to individual phonetic feature errors, which is obscured by all-or-nothing metrics like WER.
Anthology ID:
2026.africanlp-main.14
Volume:
Proceedings of the 7th Workshop on African Natural Language Processing (AfricaNLP 2026)
Month:
March
Year:
2026
Address:
Rabat, Morocco
Editors:
Everlyn Asiko Chimoto, Constantine Lignos, Shamsuddeen Muhammad, Idris Abdulmumin, Clemencia Siro, David Ifeoluwa Adelani
Venues:
AfricaNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
149–162
Language:
URL:
https://aclanthology.org/2026.africanlp-main.14/
DOI:
Bibkey:
Cite (ACL):
Fei-Yueh Chen, Lateef Adeleke, and C. M. Downey. 2026. Linguistically Informed Evaluation of Multilingual ASR for African Languages. In Proceedings of the 7th Workshop on African Natural Language Processing (AfricaNLP 2026), pages 149–162, Rabat, Morocco. Association for Computational Linguistics.
Cite (Informal):
Linguistically Informed Evaluation of Multilingual ASR for African Languages (Chen et al., AfricaNLP 2026)
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PDF:
https://aclanthology.org/2026.africanlp-main.14.pdf