Audio--Image Alignment as a Continued-Pretraining Stage Improves Low-Resource ASR

Thousands of languages are spoken worldwide, yet many remain under-resourced for Automatic Speech Recognition (ASR) due to the limited availability of high-quality transcribed speech data. Collecting accurate transcriptions is often costly and labor-intensive, particularly for low-resource languages. In this work, we investigate the use of aligned audio-image pairs to adapt pretrained audio encoders without requiring transcription data before supervised fine-tuning. Our proposed representation alignment stage is introduced between large-scale pretraining and supervised ASR fine-tuning. Specifically, image representations extracted from pretrained vision encoders are aligned with audio representations to further adapt a pretrained audio encoder. For this alignment process, we utilize the Vaani dataset, in which images serve as prompts for speech collection, naturally providing paired audio-image data. We evaluate the proposed approach using multiple vision encoders and a pretrained FastConformer audio encoder. Experimental results demonstrate that models fine-tuned after representation alignment consistently achieve improved ASR performance compared to direct fine-tuning. These findings highlight the potential of audio-image representation alignment as an effective transcription-free adaptation strategy for enhancing ASR systems in low-resource language settings.