Unsupervised Speech Recognition at the Syllable Level

Liming Wang, Kai-Wei Chang, Kunio Kashino, David Harwath, Mark A. Hasegawa-Johnson, James R. Glass


Abstract
Training speech recognizers with unpaired speech and text – known as unsupervised speech recognition (UASR) – is a crucial step toward extending ASR to low-resource languages in the long-tail distribution and enabling multimodal learning from non-parallel data. However, existing approaches based on phones often rely on costly resources such as grapheme-to-phoneme converters (G2Ps) and struggle to generalize to languages with ambiguous phoneme boundaries due to training instability. In this paper, we address both challenges by introducing a syllable-level UASR framework based on masked language modeling, which avoids the need for G2P and the instability of GAN-based methods. Our approach achieves up to a 40% relative reduction in character error rate (CER) on LibriSpeech and generalizes effectively to low-resource languages that have remained particularly difficult for prior methods. Code will be released upon acceptance.
Anthology ID:
2026.emnlp-main.90
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
2115–2135
Language:
URL:
https://aclanthology.org/2026.emnlp-main.90/
DOI:
Bibkey:
Cite (ACL):
Liming Wang, Kai-Wei Chang, Kunio Kashino, David Harwath, Mark A. Hasegawa-Johnson, and James R. Glass. 2026. Unsupervised Speech Recognition at the Syllable Level. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 2115–2135, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Unsupervised Speech Recognition at the Syllable Level (Wang et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.90.pdf