Factor Analyzed HMM Topology for Speech Recognition

This paper presents a new factor analyzed (FA) similarity measure between two Gaussian mixture models (GMMs). An adaptive hidden Markov model (HMM) topology is built to compensate the pronunciation variations in speech recognition. Our idea aims to evaluate whether the variation of a HMM state from new speech data is significant or not and judge if a new state should be generated in the models. Due to the effectiveness of FA data analysis, we measure the GMM similarity by estimating the common factors and specific factors embedded in the HMM means and variances. Similar Gaussian densities are represented by the common factors. Specific factors express the residual of similarity measure. We perform a composite hypothesis test due to common factors as well as specific factors. An adaptive HMM topology is accordingly established from continuous collection of training utterances. Experiments show that the proposed FA measure outperforms other measures with comparable size of parameters.