Application of allophonic and lexical constraints in continuous digit recognition

This paper considers the role of allophonic and lexical constraints in the recognition of continuous digit strings. We first describe a study using both narrow and broad ideal phonetic representations of digit strings for lexical access. This study suggests that allophonic and lexical constraints are very powerful in the digit recognition task. We then describe a system which segments the speech signal into broad phonetic classes and applies allophonic and lexical constraints to produce word hypotheses from a spoken digit string. The system was evaluated on three new speakers (one male and two female). After lexical access, the correct digit was not among the set of hypotheses only 1% of the time.