Since conventional Automatic Speech Recognition (ASR) systems often contain many modules and use varieties of expertise, it is hard to build and train such models. Recent research show that end-to-end ASRs can significantly simplify the speech recognition pipelines and achieve competitive performance with conventional systems. However, most end-to-end ASR systems are neither reproducible nor comparable because they use specific language models and in-house training databases which are not freely available. This is especially common for Mandarin speech recognition. In this paper, we propose a CNN+BLSTM+CTC end-to-end Mandarin ASR. This CNN+BLSTM+CTC ASR uses Convolutional Neural Net (CNN) to learn local speech features, uses Bidirectional Long-Short Time Memory (BLSTM) to learn history and future contextual information, and uses Connectionist Temporal Classification (CTC) for decoding. Our model is completely trained on the by-far-largest open-source Mandarin speech corpus AISHELL-1, using neither any in-house databases nor external language models. Experiments show that our CNN+BLSTM+CTC model achieves a WER of 19.2%, outperforming the exiting best work. Because all the data corpora we used are freely available, our model is reproducible and comparable, providing a new baseline for further Mandarin ASR research.
End-to-end Speech Recognition With Word-Based Rnn Language Models
