Phoneme Lattice Based A* Search Algorithm for Speech Recognition

This paper presents the Speeral continuous speech recognition system developed in the LIA. Speeral uses a modified A* algorithm to find in the search graph the best path taking into account acoustic and linguistic constraints. Rather than words by words, the A* used in Speeral is based on a phoneme lattice previously generated. To avoid the backtraking problems, the system keeps for each frame the deepest nodes of the partially explored lexical tree starting at this frame. If a new hypothesis to explore is ended by a word and the lexicon starting where this word finishes has already been developed, then the next hypothesis will "jump" directly to the deepest nodes. Decoding performances of Speeral are evaluated on the test set of the ARC B1 campaign of AUPELF '97. The experiments on this French database show the efficiency of the search strategy described in this paper.