We present results that show it is possible to build a competitive, greatly
simplified, large vocabulary continuous speech recognition system with whole
words as acoustic units. We model the output vocabulary of about 100,000 words
directly using deep bi-directional LSTM RNNs with CTC loss. The model is
trained on 125,000 hours of semi-supervised acoustic training data, which
enables us to alleviate the data sparsity problem for word models. We show that
the CTC word models work very well as an end-to-end all-neural speech
recognition model without the use of traditional context-dependent sub-word
phone units that require a pronunciation lexicon, and without any language
model removing the need to decode. We demonstrate that the CTC word models
perform better than a strong, more complex, state-of-the-art baseline with
sub-word units.

使用 CTC 损失和双向 LSTM RNN 网络，基于整词的声学单位构建连续语音识别系统，无需传统上下文依赖的子词单元和语言模型。

神经语音识别：基于声学到词汇 LSTM 模型的大词汇量语音识别

Neural Speech Recognizer: Acoustic-to-Word LSTM Model for Large  Vocabulary Speech Recognition

We present a method to perform first-pass large vocabulary continuous speech
recognition using only a neural network and language model. Deep neural network
acoustic models are now commonplace in HMM-based speech recognition systems,
but building such systems is a complex, domain-specific task. Recent work
demonstrated the feasibility of discarding the HMM sequence modeling framework
by directly predicting transcript text from audio. This paper extends this
approach in two ways. First, we demonstrate that a straightforward recurrent
neural network architecture can achieve a high level of accuracy. Second, we
propose and evaluate a modified prefix-search decoding algorithm. This approach
to decoding enables first-pass speech recognition with a language model,
completely unaided by the cumbersome infrastructure of HMM-based systems.
Experiments on the Wall Street Journal corpus demonstrate fairly competitive
word error rates, and the importance of bi-directional network recurrence.

本文提出了使用神经网络和语言模型进行大词汇连续语音识别的方法，并通过一种改进的前缀搜索解码算法，使得该方法完全不依赖于基于 HMM 的架构，实现了完全自主的一遍语音识别。在对华尔街日报语料库的实验中，取得了较为具有竞争力的错误率，并且证明了双向网络的重要性。