Acoustic Scores and Symbolic Mismatch Penalties in Phone Lattices

This paper builds on previous work aimed at unraveling the structure of the speech signal using probabilistic representations. The context of this work is a multi-pass speech recognition system in which a phone lattice is created and used as a basis for a lexical decoding pass (search) that allows symbolic mismatches at certain costs. The focus is on the optimization of the costs of the phone insertions, deletions and substitutions that are used in the lexical decoding pass. Two optimization approaches are presented, one related to a multi-pass computational model for human speech recognition, the other based on a decoding that minimizes Bayes´ risks. In the final section, the advantages of the two optimization methods are discussed and compared