Patent ID: 7437288

Claim:
A speech recognition apparatus using a probability model that employs a mixed distribution, said apparatus comprising: standard pattern storage means for storing a standard pattern of a Hidden Markov Model (HMM) having a plurality of states; recognition means for outputting recognition results corresponding to an input speech by using said standard pattern; standard pattern generating means for inputting learning speech and generating said standard pattern; and standard pattern adjustment means, provided between said standard pattern generating means and said standard pattern storage means, for adjusting the number of element distributions of said mixed distribution of said standard pattern; wherein said standard pattern adjustment means comprising: tree structure generating means for generating a tree structure of element distributions for each state of the HMM, and element distribution selection means for adjusting the number of element distributions of said mixed distribution of said standard pattern for each state of the HMM by selecting element distributions to leaves in said standard pattern by using said tree structure generated by said tree structure generating means after generation of said tree structure, wherein the standard pattern adjustment means calculates a description length for all possible cuts that can be made on the tree structure of element distributions, and wherein the standard pattern adjustment means selects one of the cuts having a minimum description length, in order to divide the tree structure of element distributions into a top part and a bottom part, separated by the one of the cuts.