Toward vocabulary independent telephone speech recognition

Vocabulary-independence of speech recognition systems has become an important issue because of the need for flexible vocabulary and the high cost of speech corpus collection. We outline the necessary steps to achieve the goal of vocabulary-independent speech recognition, and relate our experimental experience with telephone speech recognition. Two sets of experiments were conducted: (1) 34-command recognition, in which we compared vocabulary-independent (VI) and vocabulary-dependent (VD) systems as well as phonetic and word based systems, and (2) 42-city name recognition, in which our vocabulary independent recognition performance (8.5% W. Err.) was much better than the VI performance (18%) reported by the Oregon Graduate Institute (OGI) and very close to OGI´s VD performance (8%). We conclude that we have made some strides toward vocabulary independence, but much remains to be done; we identify the areas of improvement that are likely to lead to the goal