Deep Speech: Scaling up end-to-end speech recognition
Written for the Research library (claude-opus-5-5) from the paper text, in our own words: the license "arXiv — non-exclusive license to distribute" does not allow redistributing the text itself. Original — arxiv.org/pdf/1412.5567
Summary
Conventional speech recognizers chain together many hand-tuned components, including engineered features, acoustic models, HMMs and phoneme dictionaries. They also tend to degrade badly in noise. Baidu's Deep Speech replaces most of this chain with one recurrent network that converts spectrograms straight into English characters. It is trained with the CTC loss, so transcripts need no prior alignment to the audio. The architecture is deliberately plain so that it runs efficiently across multiple GPUs: three feed-forward layers with clipped ReLU, one bidirectional recurrent layer without LSTM gates, then a further dense layer and a softmax. The authors gathered thousands of hours of speech and synthesized extra examples containing noise and the Lombard effect, so the model could learn robustness from data alone. At decoding time, an N-gram language model is combined with the network through beam search. The system reached 16.0% error on the full Switchboard Hub5'00 test set, the best published figure at the time. It also beat commercial APIs on noisy audio. The work showed that scale in data and compute could rival elaborate engineered pipelines.
Key points
- Model and training: The 5-layer RNN has roughly 5 billion connections when unrolled over a typical utterance. Training uses CTC loss, Nesterov momentum of 0.99, and 5–10% dropout applied only to the non-recurrent layers. Test-time accuracy is improved by averaging over ensembles and over audio shifted by 5 ms.
- Language model: A KenLM N-gram model was built from 220 million phrases with a vocabulary of 495,000 words. Decoding uses beams of 1000–8000.
- Switchboard result: Deep Speech reached 16.0% WER on the full Hub5'00 test set.
- Noisy speech result: On the authors' own noisy test set, Deep Speech scored 19.06% WER. The strongest commercial competitor, Google API, scored 30.47%. The other systems compared were Apple Dictation, Bing Speech and wit.ai.
- Effect of noise synthesis: Adding synthesized noise to 5000 hours of training data cut noisy-utterance WER from 28.7% to 22.6%. Clean-speech accuracy stayed about the same.
Cited by
- Common Voice: A Massively-Multilingual Speech Corpus
- Attention-Based Models for Speech Recognition
- SpecAugment: A Simple Data Augmentation Method for Automatic Speech Recognition
- Unsupervised Data Augmentation for Consistency Training
Cite
@misc{hannun2014deep,
title = {{Deep Speech: Scaling up end-to-end speech recognition}},
author = {Hannun, Awni and Case, Carl and Casper, Jared and Catanzaro, Bryan and Diamos, Greg and Elsen, Erich and Prenger, Ryan and Satheesh, Sanjeev and Sengupta, Shubho and Coates, Adam and Ng, Andrew Y.},
year = {2014},
doi = {10.48550/arxiv.1412.5567},
eprint = {1412.5567},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.1412.5567}
}References
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