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About this paper

Rongqing Huang, Ossama Abdel-hamid, Xinwei Li, Gunnar Evermann

Researchers at Apple enhanced end-to-end Automatic Speech Recognition (ASR) systems by integrating dynamic contextual information and improving rare word recognition, achieving a 70.6% relative Word Error Rate (WER) reduction on named entities without degrading performance on general vocabulary. The approach combines class language model training, contextual Finite-State Transducers (FSTs) with score normalization, and a pronunciation-based word mapping technique.

Key insights

  • Training E2E models with class LM tags alone can improve both general and named entity-specific recognition by learning structural transitions.
  • Score normalization is crucial to prevent "anti-biasing" effects, allowing strong contextual biasing for named entities without degrading accuracy on regular utterances.
  • Leveraging phonetic similarity through word mapping can effectively address the challenge of recognizing rare or OOV named entities by transforming them into more common, pronouncible subword sequences.
  • Explicit linguistic knowledge, like FSTs and pronunciation lexicons, can be harmoniously integrated into E2E ASR systems to overcome their inherent limitations in handling dynamic context.

Summary by alphaXiv.

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