Digital Processing for Speech Coding, Synthesis and Recognition

This paper presents an overview of the current activities in speech research. We will discuss the state of the art in speech coding, text-to-speech synthesis, speech recognition, and speaker recognition. In the speech coding area, current algorithms perform well at bit rates down to 9.6 kb/s, and the research is directed at bringing the rate for high-quality speech coding down to 2.4 kb/s. In text-to-speech synthesis, what we currently are able to produce is very intelligible but not yet completely natural. Current research aims at providing higher quality and intelligibility to the synthetic speech that these systems produce. Finally, today's systems for speech and speaker recognition provide excellent performance on limited tasks; i.e. , limited vocabulary, modest syntax, small talker populations, constrained inputs, etc. Current research is directed at solving the problem of continuous speech recognition for large vocabularies, and at verifying talkers' identities from a limited amount of spoken text.