AURA-ST: Acoustic-Unconstrained Residual Architecture for Speech Translation

Barathi Ganesh HB, Michal Ptaszynski, Jairam R, Reshma Unnikrishnan


Abstract
We present AURA-ST, a three-stage modular pipeline for low-resource speech-to-text translation submitted to the IWSLT 2026 African-Celtic Track 1. The architecture bypasses traditional cross-attention between audio and text modalities by treating projected acoustic representations as a native token prefix to a frozen large language model. A dual-stream encoder captures linguistic and paralinguistic features via a jointly trained semantic and a paralinguistic encoder. A convolutional subsampler then bridges the modality gap through a 4x temporal compression and a linear projection into the LLM embedding space. Finally, a MLP-targeted Low-Rank Adaptation adapter fine-tunes the frozen Gemma-4-E2B backbone for translation without catastrophic forgetting of base language model knowledge. We further identify and resolve the incompatibility between standard PEFT attention-level adapter injection and the Gemma-4 Per-Layer Embedding architecture that tends to cause gradient isolation. Trained on the IWSLT 2026 Track 1 data covering Hausa, Igbo, and Yoruba, the final system achieves a best proxy teacher-forced SacreBLEU of 91.29 on the validation set at Phase 3, with Phase 1 speech encoder validation loss converging to 0.651.
Anthology ID:
2026.iwslt-1.28
Volume:
Proceedings of the 23rd International Conference on Spoken Language Translation (IWSLT 2026)
Month:
July
Year:
2026
Address:
San Diego, USA (in-person and online)
Editors:
Elizabeth Salesky, Antonios Anastasopoulos, Matteo Negri, Marcello Federico
Venues:
IWSLT | WS
SIG:
SIGSLT
Publisher:
Association for Computational Linguistics
Note:
Pages:
247–254
Language:
URL:
https://aclanthology.org/2026.iwslt-1.28/
DOI:
Bibkey:
Cite (ACL):
Barathi Ganesh HB, Michal Ptaszynski, Jairam R, and Reshma Unnikrishnan. 2026. AURA-ST: Acoustic-Unconstrained Residual Architecture for Speech Translation. In Proceedings of the 23rd International Conference on Spoken Language Translation (IWSLT 2026), pages 247–254, San Diego, USA (in-person and online). Association for Computational Linguistics.
Cite (Informal):
AURA-ST: Acoustic-Unconstrained Residual Architecture for Speech Translation (HB et al., IWSLT 2026)
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PDF:
https://aclanthology.org/2026.iwslt-1.28.pdf