Recent improvements to the harpy connected speech recognition system

Harpy is a program that is able to interpret a digitized speech signal to generate the corresponding sequence of words. It has been operational since 1976 and was demonstrated at the end of an ARPA sponsored five-year research program for a 1000 word vocabulary connected speech recognition task. Harpy was the only system to meet and exceed the performance goals set at the beginning of the five-year period and since 1976 it has been continuously improved. The purpose of this paper is to introduce the main problems faced while improving the characteristics of the system, to describe the partial solutions to these problems that have been already explored and to discuss the more difficult problems that have not been tackled yet and their possible solutions.