An Unanchored Matching Algorithm for Lexical Access
Describes the lexical access component of the Carnegie-Mellon University (CMU) continuous speech recognition system. The word recognition algorithm operates in a left to right fashion, building words as it traverses an input network. Search is initiated at each node in the input network. The score assigned to a word is a function of both arc phone probabilities assigned by the acoustic phonetic module and knowledge of expected phone duration and frequency of occurrence of different word pronunciations. The algorithm also incorporates knowledge-based strategies to control the number of hypotheses generated by the matcher. These strategies use criteria external to the search. Performance characteristics are reported using a 1029 word lexicon built automatically from standard pronunciation base forms by context-dependent phonetic rules. Lexical rules are independent of specific lexicons and are derived by examination of transcribed speech data. The lexical representation now includes juncture rules that model specific inter-word phenomena. A junction validation module is also described, whose task is to evaluate the connectivity of words in the word hypotheses lattice.