Continuous topic language modeling for speech recognition

Continuous representation of word sequence can effectively solve data sparseness problem in n-gram language model, where the discrete variables of words are represented and the unseen events are prone to happen. This problem is increasingly severe when extracting long-distance regularities for high-order n-gram model. Rather than considering discrete word space, we construct the continuous space of word sequence where the latent topic information is extracted. The continuous vector is formed by the topic posterior probabilities and the least-squares projection matrix from discrete word space to continuous topic space is estimated accordingly. The unseen words can be predicted through the new continuous latent topic language model. In the experiments on continuous speech recognition, we obtain significant performance improvement over the conventional topic-based language model.