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RESEARCH PAPER / 2026-05-14

Mind the Gap: Impact of Synthetic Conversational Data on Multi-Talker ASR and Speaker Diarization

Alexander Polok, Ivan Medennikov, Jan Černocký, ★ Shinji Watanabe ...Full author list in the original paper.

Carnegie Mellon University +2 · arXiv

Affiliations: Brno University of Technology, Carnegie Mellon University, NVIDIA

Abstract

Recent breakthroughs in multi-talker ASR (MT-ASR) and speaker diarization (SD) rely on synthetic data to mitigate the scarcity of large-scale conversational recordings, yet the impact of specific simulation choices remains poorly understood. To mind the gap between simulated mixtures and real-world interactions, we present a study of synthetic data generation for leading MT-ASR (DiCoW) and SD (Sortformer) systems. By introducing FastMSS, a highly efficient open-source simulator, we analyze turn-taking dynamics, source domain, acoustic augmentation, and data mixing strategies. Our findings reveal that optimal simulation recipes are highly task-dependent: increasing speech overlap benefits ASR but degrades diarization. Furthermore, broad source diversity consistently outperforms exact domain matching. Ultimately, synthetic-only training approaches real-data baselines, and combining simulated data with real recordings yields substantial gains over real-only training across both tasks.

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 paper presents a comprehensive study on the impact of synthetic conversational data on multi-talker ASR and speaker diarization, revealing critical insights into simulation strategies and their task-dependent effects. The introduction of FastMSS as an open-source toolkit represents a significant advancement in the field, enabling further research and application in multi-talker speech processing.

Methodology

The paper introduces FastMSS, an open-source simulator that allows for the generation of synthetic multi-talker conversations with configurable parameters. The methodology is robust, systematically varying key factors such as turn-taking dynamics and source domain diversity. The authors provide a clear rationale for their choices and demonstrate the importance of task-specific simulation strategies, which is a significant contribution to the field. The use of two leading models, DiCoW for MT-ASR and Sortformer for SD, adds depth to the analysis, allowing for a comprehensive understanding of how synthetic data can be optimized for different tasks.

Results & evaluation

The experiments are well-designed, utilizing a variety of datasets that reflect real-world conditions. The results are clearly presented, showing the impact of different simulation strategies on performance metrics such as tcpWER for ASR and DER for diarization. The findings that synthetic data can approach real-data performance and that combining both yields the best results are particularly noteworthy. The paper effectively demonstrates the practical implications of its findings, making it relevant for both academic and industry applications.

Reproducibility

The authors emphasize reproducibility by releasing FastMSS as an open-source toolkit, which is a commendable practice in the research community. They provide detailed descriptions of their experimental setup, including datasets and evaluation metrics, which further enhances the reproducibility of their results. However, the reliance on specific configurations and hyperparameters may require careful attention from users to replicate the results exactly.

Limitations

One limitation noted in the paper is the potential lack of inter-turn semantic coherence in the generated conversations, which could affect the performance of ASR systems. Additionally, while the study covers a range of simulation strategies, the generalizability of the findings to other tasks or domains outside those tested remains uncertain. The paper could also benefit from a more extensive discussion on the ethical implications of using synthetic data in real-world applications.

Broader impact

The research has significant implications for the fields of speech recognition and speaker diarization, particularly in scenarios where real conversational data is scarce. By demonstrating that synthetic data can effectively complement or even substitute real data, this work opens avenues for more efficient training of ASR and diarization systems. The findings could lead to advancements in applications such as virtual assistants, automated meeting transcriptions, and other multi-talker environments. The paper presents a comprehensive study on the impact of synthetic conversational data on multi-talker ASR and speaker diarization, revealing critical insights into simulation strategies and their task-dependent effects. The introduction of FastMSS as an open-source toolkit represents a significant advancement in the field, enabling further research and application in multi-talker speech processing.

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