Abstract:
A speech recognizer includes a feature extracting unit for analyzing an input speech to extract a feature vector of the input speech. A speech data memory stores speech data and symbol trains of the input speech. A reference pattern memory stores sets each of a given partial symbol train of a word presented for recognition and an index of speech data with the expression thereof containing the partial symbol train in the speech data memory. A distance calculating unit reads out speech data corresponding to a partial symbol train stored in the reference pattern memory from the speech data memory, and calculates a distance between the partial symbol train read out from the reference pattern memory and a particular section of the input speech. A pattern matching unit derives, with respect to each word presented for recognition, a division of the subject word interval which minimizes the sum of distances of the input speech sections over an entire word interval. A recognition result calculating unit outputs, as a recognition result, a word presented for recognition, which gives the minimum one of the distances between the input speech data output of the pattern matching unit and all the words presented for recognition.
Abstract:
A speech recognition method according to the present invention uses distances calculated through a variance weighting process using covariance matrixes as the local distances (prediction residuals) between the feature vectors of input syllables/sound elements and predicted vectors formed by different statuses of reference neural prediction models (NPM's) using finite status transition networks. The category to minimize the accumulated value of these local distances along the status transitions of all the prediction models is figured out by dynamic programming, and used as the recognition output. Learning of the reference prediction models used in this recognition method is accomplished by repeating said distance calculating process and the process to correct the parameters of the different statuses and the covariance matrixes of said prediction models in the direction of reducing the distance between the learning patterns whose category is known and the prediction models of the same category as this known category, and what have satisfied prescribed conditions of convergence through these calculating and correcting processes are determined as reference pattern models.
Abstract:
A first parameter set constituting reference patterns of each category in speech recognition based on pattern matching with a reference pattern is to be determined from a plurality of learning utterance data. The first parameter set is determined so that a third evaluation function, represented by a sum of a first evaluation function and a second evaluation function is maximized. The first evaluation function represents a matching degree between all learning utterances and corresponding reference patterns. The second evaluation function represents a matching degree between elements of the first parameter set.