Review of the ARPA Speech Understanding Project

Abstract

In September of 1976, four speech understanding systems were demonstrated, signifying the end of a five‐year program of research and development sponsored by the Advanced Research Projects Agency (ARPA). The best performance was displayed by the Harpy system developed at Carnegie–Mellon University. Harpy satisfied a set of design goals that were specified at the beginning of the program, including the gal of understanding over 90% of a set of naturally spoken sentences composed from a 1000‐word lexicon. After defining the nature of the speech understanding problem, the four systems are described and critically evaluated. Based on this review, a structure for a next‐generation speech understanding system is proposed and parts of it are considered as a possible model of the early stages of speech perception. The perceptual model addresses the issue of lexical access and includes a decoding network composed of expected spectral sequences for all word strings of English.