Hidden markov model generation apparatus and method with selection of number of states

Abstract

A model generation unit () is provided. The model generation unit includes an alignment module () arranged to receive pairs of sequences of parameter frame vectors from a buffer () and to perform dynamic time warping of the parameter frame vectors to align corresponding parts of the pair of utterances. A consistency checking module () is provided to determine whether the aligned parameter frame vectors correspond to the same word. If this is the case the aligned parameter frame vectors are passed to a clustering module () which groups the parameter frame vectors into a number of clusters. Whilst clustering the parameter frame vectors, the clustering module () determines for each grouping an objective function calculating the best fit of a model to the clusters per degrees of freedom of that model. When the best fit per degrees of freedom is determined, the parameter frame vectors are passed to a hidden Markov model generator () which generates a hidden Markov model having states corresponding to the clusters determined to have the best fit per degrees of freedom.