Latent Semantic Rational Kernels for Topic Spotting on Conversational Speech

In this work, we propose latent semantic rational kernels (LSRK) for topic spotting on conversational speech. Rather than mapping the input weighted finite-state transducers (WFSTs) onto a high dimensional n-gram feature space as in n-gram rational kernels, the proposed LSRK maps the WFSTs onto a latent semantic space. With the proposed LSRK, all available external knowledge and techniques can be flexibly integrated into a unified WFST based framework to boost the topic spotting performance. We present how to generalize the LSRK using tf-idf weighting, latent semantic analysis, WordNet and probabilistic topic models. To validate the proposed LSRK framework, we conduct the topic spotting experiments on two datasets, Switchboard and AT&T HMIHY0300 initial collection. The experimental results show that with the proposed LSRK we can achieve significant and consistent topic spotting performance gains over the n-gram rational kernels.