Gold-Preserving Synthetic Augmentation for Verbatim Swedish Automatic Speech Recognition

Giuseppe Chiriatti, Dimitrios Kokkinakis, Flavio Bertini, Ricardo Muñoz Sánchez, Herbert Lange


Abstract
Verbatim transcripts, which keep the hesitations and interactional particles that ordinary automatic speech recognition (ASR) removes, are a prerequisite for speech-based cognitive assessment, and they are hardest to obtain for languages with little annotated speech. We study this problem for Swedish with a 1.02-hour corpus of manually transcribed spontaneous speech, too small for full fine-tuning of KB-Whisper-large. We adapt the model with a low-rank adapter and compare three ways of extending the training data: pseudo-labeling of untranscribed in-domain audio, unguided synthesis with a language model and a text-to-speech system, and a gold-preserving pipeline that reproduces the disfluency distribution of the gold corpus by construction and can be audited before training. Fine-tuning reduces disfluency-segment word error rate (WER) by 32% relative, with blockwise-bootstrap confidence intervals disjoint from the zero-shot baseline, while the three augmentation strategies are not separable by WER across five seeds. The gold-preserving pipeline needs no untranscribed audio, and its disfluency distribution can be verified in advance.
Anthology ID:
2026.salma-1.4
Volume:
The Proceedings of Speech and Audio Language Models Workshop (2nd Edition)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Santosh T.Y.S.S., Sreyan Ghosh, Ramani Duraiswami, Shinji Watanabe, Siddhant Arora, Sonal Kumar, Yossi Adi, Dinesh Manocha, Leibny Paola Garcia Perera
Venues:
SALMA | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
38–44
Language:
URL:
https://aclanthology.org/2026.salma-1.4/
DOI:
Bibkey:
Cite (ACL):
Giuseppe Chiriatti, Dimitrios Kokkinakis, Flavio Bertini, Ricardo Muñoz Sánchez, and Herbert Lange. 2026. Gold-Preserving Synthetic Augmentation for Verbatim Swedish Automatic Speech Recognition. In The Proceedings of Speech and Audio Language Models Workshop (2nd Edition), pages 38–44, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Gold-Preserving Synthetic Augmentation for Verbatim Swedish Automatic Speech Recognition (Chiriatti et al., SALMA 2026)
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PDF:
https://aclanthology.org/2026.salma-1.4.pdf