1. Apparatus for recognizing a speech pattern as a string of predetermined reference words comprising: means for storing a set of signals representative of the time frame sequence of acoustic features of each reference word, said time frame sequence having a beginning frame and an ending frame; means for producing a set of signals representative of the time frame sequence of acoustic features of said speech pattern, means responsive to the speech pattern acoustic feature signals and the reference word acoustic feature signals for generating a plurality of reference word strings, and means for identifying the speech pattern as one of the generated reference word strings, characterized in that said reference word string generating means comprises; means for generating a set of signals for identifying successive reference word levels, means for assigning a segment of said speech pattern to each successive level, means operative in each successive level for time registering the level speech pattern segment feature signals with the reference word feature signals to produce level time registration speech pattern segment endframe signals and time registration correspondence signals for said reference words, and means responsive to the time registration endframe and time registration correspondence signals of the levels for selecting reference word strings.