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Senior Research Engineer - Voice

AI / ML Engineer • Senior • Remote • Full-time • 📍 Europe

Synthesia is the world's leading AI video platform for business, used by over 90% of the Fortune 100. Founded in 2017 and headquartered in London, with offices across Europe and the US. After a Series E round raising $200M, its valuation stands at $4B. As a Research Engineer in the Audio Post-Training Team (part of a 40+ person R&D department) you work on generative speech and voice synthesis - creating high-quality, expressive and real-time synthetic voices and ensuring the in-house voice models reach production-level quality, speed and robustness. Your work directly impacts solutions used by over 60,000 businesses. The role is remote in Europe.

Stack

Responsibilities

  • Develop and evaluate streaming and speech-to-speech systems for low-latency, interactive voice synthesis
  • Adapt models for new conditioning inputs (emotion, speed, prosody, speaker control, etc.)
  • Implement post-training optimization techniques (quantization, pruning, distillation) to improve efficiency and latency in real-time speech generation
  • Integrate and test novel architectures such as neural codecs, diffusion or flow-matching models to enhance realism and responsiveness
  • Contribute to defining new evaluation metrics for conversational speech, including latency-aware and online MOS prediction systems
  • Stay updated with the latest research in audio diffusion, autoregressive models, neural codecs and multimodal LLMs
  • Apply DPO (Direct Preference Optimization) and distillation to fine-tune large-scale speech models

Requirements

  • Strong understanding of generative modeling, ideally applied to sequential or multimodal data
  • Hands-on experience with large language models (LLMs) or similar transformer-based architectures
  • High proficiency in PyTorch, including distributed training and model optimization
  • Solid grasp of time-series modeling and tokenization, preferably for audio or speech
  • Demonstrated ability to prototype quickly, test hypotheses and iterate efficiently
  • Proven experience training deep learning models end-to-end, from data preparation to evaluation
  • Strong general software engineering skills to contribute to a large, shared research infrastructure

Nice to have

  • Experience with real-time or streaming architectures
  • Familiarity with state-of-the-art audio and speech generation architectures (diffusion models, neural codecs, flow-matching models, autoregressive decoders)
  • Experience with speech-to-speech or text-to-speech (TTS) systems
  • Original research contributions, such as publications or open-source work in top-tier venues (ICASSP, Interspeech, NeurIPS, ICML)

Soft skills

Quick prototyping and efficient iterationCollaborative within a large, shared research infrastructure