Patent ID: 7565290
Filing Date: 2009-07-21
Classification: G10L

Abstract:
1. A speech recognition apparatus comprising: (a) a memory for storing: (i) a word dictionary having recognition target words, said word dictionary comprising a tree structure in which the recognition target words share a predetermined speech unit; (ii) a first acoustic model which expresses a reference pattern of the speech unit by one or more states; and (iii) a second acoustic model which is lower in precision than said first acoustic model; (b) selection means for selecting a state of interest from the tree structure; (c) checking means for checking the number of branches of the selected state; and (d) likelihood calculation means for calculating a likelihood of an acoustic feature parameter for states immediately succeeding the selected state using the first acoustic model, if the number of branches of the selected state is equal to or more than a predetermined value, and otherwise calculating a likelihood of an acoustic feature parameter for states immediately succeeding the selected state using the second acoustic model; wherein in calculating a likelihood with respect to a state of interest by using said second acoustic model, if likelihood calculation using said first acoustic model has been performed for a state having the same speech unit alignment as that of the state of interest, said likelihood calculation means reuses a result of the likelihood calculation as a result of likelihood calculation for the state of interest.