ToneCL:Contrastive Learning for Few-Shot Syllable-Level Tone Classification

Qisheng Liao, Youngah Do


Abstract
Tone languages constitute over 50-70% of the world’s languages, but the vast majority are low-resource, lacking the large transcribed corpora needed for automatic tone classification. Existing datasets are typically collected at the sentence level, whereas field linguists require fine-grained syllable-level annotations. We propose ToneCL, a lightweight contrastive learning framework for few-shot syllable-level tone classification. We simulate low-resource conditions on Mandarin and Vietnamese, limiting labeled data to tens of examples per tone class. ToneCL is pretrained on unlabeled speech with augmentations that preserve tonal identity, then fine-tuned on few-shot examples. Experiments show our method consistently outperforms baselines, achieving 91.6% on six-speaker Mandarin at 10 shots. Cross-lingual transfer is also effective: pretraining on Vietnamese and fine-tuning on Mandarin reaches 91.0% accuracy at 10 shots. Ablation confirms that frequency band rejection is the most critical augmentation.
Anthology ID:
2026.aacl-long.69
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1513–1525
Language:
URL:
https://aclanthology.org/2026.aacl-long.69/
DOI:
Bibkey:
Cite (ACL):
Qisheng Liao and Youngah Do. 2026. ToneCL:Contrastive Learning for Few-Shot Syllable-Level Tone Classification. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 1513–1525, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
ToneCL:Contrastive Learning for Few-Shot Syllable-Level Tone Classification (Liao & Do, AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-long.69.pdf