Lost in Compression: Calibration Bias and the Accent-WER Gap in Speech LLMs

Angad Ripudaman Singh Bajwa


Abstract
GPTQ and similar calibration-based quantization methods tune their rounding to a small calibration sample, in practice usually convenient, native-accented read speech. Edge devices disproportionately run quantized models, so the speakers most likely to depend on the compressed model are often the ones calibration represented least. Compression is known to amplify bias in text LLMs and across languages in multilingual speech models, but whether it does so within a single language, between native and non-native accents, in a modern speech LLM, remains untested. We quantize the LLM backbone of Qwen2-Audio-7B-Instruct with GPTQ, hold the recipe fixed and vary only which EdAcc speakers fill the calibration set (native-only, balanced, L2-only), measuring the native-vs-L2 word error rate (WER) gap at matched overall WER. We expected nativeonly calibration to widen the gap and balanced calibration to close it. Instead, homogeneous calibration, native-only or L2-only, narrows the gap while balanced calibration does almost nothing. It recurs when we quantize the audio encoder, weakens at 3-bit and collapses at 2-bit.
Anthology ID:
2026.impactspeech-1.6
Volume:
Proceedings of the IMPACT-SPEECH Workshop: Identifying, Measuring, Preventing, and Assessing Consequences of Bias in Speech LLMs
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Ravi Shekhar, Monorama Swain, Jagabandhu Mishra, Sandipan Dhar, Haralambos Mouratidis, Matthew Purver
Venues:
IMPACT-SPEECH | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
61–66
Language:
URL:
https://aclanthology.org/2026.impactspeech-1.6/
DOI:
Bibkey:
Cite (ACL):
Angad Ripudaman Singh Bajwa. 2026. Lost in Compression: Calibration Bias and the Accent-WER Gap in Speech LLMs. In Proceedings of the IMPACT-SPEECH Workshop: Identifying, Measuring, Preventing, and Assessing Consequences of Bias in Speech LLMs, pages 61–66, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Lost in Compression: Calibration Bias and the Accent-WER Gap in Speech LLMs (Bajwa, IMPACT-SPEECH 2026)
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PDF:
https://aclanthology.org/2026.impactspeech-1.6.pdf