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RESEARCH PAPER / 2026-06-11

NaturalFlow: Reducing Disruptive Pauses for Natural Speech Flow in Simultaneous Speech-to-Speech Translation

Dongwook Lee, Youngho Cho, Sangkwon Park ...Full author list in the original paper.

Seoul National University +1 · Proceedings of the 26th Interspeech Conference, Long Paper

Affiliations: Seoul National University, University of Seoul

Abstract

Simultaneous speech-to-speech translation aims to enable near-real-time communication by minimizing latency, offering a compelling, real-time alternative to the high latency of consecutive translation. However, the excessive pursuit of low latency often results in fragmented chunk-wise speech. Consequently, listeners are subjected to an unnatural acoustic flow punctuated by frequent pauses, which could increase their cognitive load. To bridge this gap, we introduce a fluency-aware optimization framework designed to discover the sweet spot between the low-latency benefits of simultaneous translation and the natural flow of consecutive translation. Our framework minimizes inter-chunk silences by leveraging model-internal signals, including linguistic diversity and induced temporal variability in speech durations. Experiments on short- and long-form benchmarks show that our framework produces natural speech flow while maintaining competitive latency and translation quality.

The following analysis is generated by AI and may contain errors. It is separate from the authors’ abstract and is not peer review.

Research summary

The main contribution of this paper is the introduction of a fluency-aware optimization framework for simultaneous speech-to-speech translation that effectively reduces disruptive pauses while preserving translation fidelity. This work represents a significant advancement in the field, addressing a critical gap in existing translation systems and providing a robust methodology that balances fluency and accuracy in real-time communication.

Methodology

The proposed methodology introduces a fluency-aware optimization framework, which is innovative in its approach to simultaneous speech-to-speech translation (S2ST). By leveraging model-internal signals and preference-based learning, the authors effectively address the challenge of reducing disruptive pauses while maintaining translation quality. The use of Direct Preference Optimization (DPO) and the novel Silver-Medal Preference strategy are particularly noteworthy, as they allow for a balanced trade-off between fluency and fidelity, which is a significant advancement in the field. The methodology is well-structured, with clear definitions of the optimization objectives and a robust preference data construction pipeline.

Results & evaluation

The experiments are comprehensive, utilizing multiple benchmarks (CVSS-C, VoxPopuli, mTEDx, and Audio-NTREX) that cover both short- and long-form speech. The results demonstrate that NaturalFlow successfully reduces silence ratios while maintaining competitive translation quality and latency metrics. The inclusion of human evaluations adds credibility to the findings, as it confirms that listeners prefer the natural flow of the translations produced by the proposed model. The comparison against established baselines like Seamless and Hibiki provides a solid context for assessing the improvements achieved.

Reproducibility

The paper provides sufficient detail regarding the experimental setup, including the architecture, training procedures, and evaluation metrics. However, the reproducibility could be enhanced by providing access to the code and datasets used in the experiments. The absence of a public repository limits the ability of other researchers to replicate the results fully.

Limitations

One limitation is the potential overfitting to the specific datasets used for training and evaluation. While the model shows promising results on the selected benchmarks, its performance on unseen data or in real-world applications remains to be validated. Additionally, the reliance on human evaluators for assessing fluency may introduce variability that could affect the consistency of the results.

Broader impact

The implications of this research are significant for the fields of machine translation and human-computer interaction, particularly in applications requiring real-time communication across language barriers. By improving the fluency of simultaneous speech translations, the framework could enhance user experience in various contexts, such as international conferences, diplomatic meetings, and customer service interactions. This work lays the groundwork for future developments in more natural and effective speech translation systems. The main contribution of this paper is the introduction of a fluency-aware optimization framework for simultaneous speech-to-speech translation that effectively reduces disruptive pauses while preserving translation fidelity. This work represents a significant advancement in the field, addressing a critical gap in existing translation systems and providing a robust methodology that balances fluency and accuracy in real-time communication.

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