Decoder-only Conformer with Modality-aware Sparse Mixtures of Experts for ASR

Fuente: arXiv
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Autores principales: Lee, Jaeyoung, Mimura, Masato
Formato: Preprint
Publicado: 2026
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author Lee, Jaeyoung
Mimura, Masato
author_facet Lee, Jaeyoung
Mimura, Masato
contents We present a decoder-only Conformer for automatic speech recognition (ASR) that processes speech and text in a single stack without external speech encoders or pretrained large language models (LLM). The model uses a modality-aware sparse mixture of experts (MoE): disjoint expert pools for speech and text with hard routing and top-1 selection, embedded in hybrid-causality Conformer blocks (bidirectional for speech, causal for text). Training combines CTC on speech positions with label-smoothed cross-entropy for text generation. Our 113M-parameter model consistently improves WER over a 139M AED baseline on Librispeech (2.8% vs. 3.2% test-clean; 5.6% vs. 6.0% test-other). On Common Voice 16.1 with a single multilingual model across five languages, our approach reduces average WER from 12.2% to 10.6%. To our knowledge, this is the first randomly initialized decoder-only ASR that surpasses strong AED baselines via modality-aware routing and sparse MoE, achieving better accuracy with fewer active parameters and without alignment/adaptation modules.
format Preprint
id arxiv_https___arxiv_org_abs_2602_12546
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Decoder-only Conformer with Modality-aware Sparse Mixtures of Experts for ASR
Lee, Jaeyoung
Mimura, Masato
Audio and Speech Processing
Artificial Intelligence
Computation and Language
Sound
We present a decoder-only Conformer for automatic speech recognition (ASR) that processes speech and text in a single stack without external speech encoders or pretrained large language models (LLM). The model uses a modality-aware sparse mixture of experts (MoE): disjoint expert pools for speech and text with hard routing and top-1 selection, embedded in hybrid-causality Conformer blocks (bidirectional for speech, causal for text). Training combines CTC on speech positions with label-smoothed cross-entropy for text generation. Our 113M-parameter model consistently improves WER over a 139M AED baseline on Librispeech (2.8% vs. 3.2% test-clean; 5.6% vs. 6.0% test-other). On Common Voice 16.1 with a single multilingual model across five languages, our approach reduces average WER from 12.2% to 10.6%. To our knowledge, this is the first randomly initialized decoder-only ASR that surpasses strong AED baselines via modality-aware routing and sparse MoE, achieving better accuracy with fewer active parameters and without alignment/adaptation modules.
title Decoder-only Conformer with Modality-aware Sparse Mixtures of Experts for ASR
topic Audio and Speech Processing
Artificial Intelligence
Computation and Language
Sound
url https://arxiv.org/abs/2602.12546