Closing the Speech-Text Gap with Limited Audio for Effective Domain Adaptation in LLM-Based ASR

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Main Authors: Bañeras-Roux, Thibault, Burdisso, Sergio, Villatoro-Tello, Esaú, Sánchez-Cortés, Dairazalia, Liu, Shiran, Baroudi, Severin, Kumar, Shashi, Watawana, Hasindri, E, Manjunath K, Hacioglu, Kadri, Motlicek, Petr, Stolcke, Andreas
Format: Preprint
Published: 2026
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author Bañeras-Roux, Thibault
Burdisso, Sergio
Villatoro-Tello, Esaú
Sánchez-Cortés, Dairazalia
Liu, Shiran
Baroudi, Severin
Kumar, Shashi
Watawana, Hasindri
E, Manjunath K
Hacioglu, Kadri
Motlicek, Petr
Stolcke, Andreas
author_facet Bañeras-Roux, Thibault
Burdisso, Sergio
Villatoro-Tello, Esaú
Sánchez-Cortés, Dairazalia
Liu, Shiran
Baroudi, Severin
Kumar, Shashi
Watawana, Hasindri
E, Manjunath K
Hacioglu, Kadri
Motlicek, Petr
Stolcke, Andreas
contents Conventional end-to-end automatic speech recognition (ASR) systems rely on paired speech-text data for domain adaptation. Recent LLM-based ASR architectures connect a speech encoder to a large language model via a projection module, enabling adaptation with text-only data. However, this introduces a modality gap, as the LLM is not exposed to the noisy representations produced by the speech projector. We investigate whether small amounts of speech can mitigate this mismatch. We compare three strategies: text-only adaptation, paired speech-text adaptation, and mixed batching (MB), which combines both. Experiments in in-domain and out-of-domain settings show that even limited speech consistently improves performance. Notably, MB using only 10% of the target-domain (less than 4 hours) speech achieves word error rates comparable to, or better than, conventional ASR fine-tuning with the full dataset, indicating that small amounts of speech provide a strong modality-alignment signal.
format Preprint
id arxiv_https___arxiv_org_abs_2604_06487
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Closing the Speech-Text Gap with Limited Audio for Effective Domain Adaptation in LLM-Based ASR
Bañeras-Roux, Thibault
Burdisso, Sergio
Villatoro-Tello, Esaú
Sánchez-Cortés, Dairazalia
Liu, Shiran
Baroudi, Severin
Kumar, Shashi
Watawana, Hasindri
E, Manjunath K
Hacioglu, Kadri
Motlicek, Petr
Stolcke, Andreas
Computation and Language
Conventional end-to-end automatic speech recognition (ASR) systems rely on paired speech-text data for domain adaptation. Recent LLM-based ASR architectures connect a speech encoder to a large language model via a projection module, enabling adaptation with text-only data. However, this introduces a modality gap, as the LLM is not exposed to the noisy representations produced by the speech projector. We investigate whether small amounts of speech can mitigate this mismatch. We compare three strategies: text-only adaptation, paired speech-text adaptation, and mixed batching (MB), which combines both. Experiments in in-domain and out-of-domain settings show that even limited speech consistently improves performance. Notably, MB using only 10% of the target-domain (less than 4 hours) speech achieves word error rates comparable to, or better than, conventional ASR fine-tuning with the full dataset, indicating that small amounts of speech provide a strong modality-alignment signal.
title Closing the Speech-Text Gap with Limited Audio for Effective Domain Adaptation in LLM-Based ASR
topic Computation and Language
url https://arxiv.org/abs/2604.06487