Speech recognition apparatus for recognizing the category of an input

Abstract

A speech recognition apparatus is adapted to previously prepare a noise pattern in response to environmental noise prior to inputting a speech signal, evaluate a speech feature vector B.sub.i yielded by subtracting the noise pattern from a feature vector A.sub.i of the input speech upon inputting the speech signal thereafter, spectrum-normalize the speech feature vector B.sub.i, evaluate a local peaks vector by making use of binary-coding processing wherein only a component of a channel being the maximum of the spectrum-normalized vector in a direction of frequency is assumed to be '1', evaluate pattern similarity between an input pattern comprising a local peaks vector from the start point to the end point of the input speech and previously prepared reference patterns of a plurality of categories of the same format as the input pattern, and judge a category of a reference pattern being the maximum among the pattern similarities as a recognized result. As a result, any influence of environmental noise on the speech of concern is eliminated for assuring highly accurate recognition. Furthermore, the speech recognition apparatus is adapted to improve the efficiency and accuracy of speech recognition by evaluating a new speech feature vector of a prescribed frame number by effecting linear expansion therefor on the basis of internal division for adjoining speech feature vectors B.sub.i and B.sub.i +1, and smoothing a local peaks vector.