Present Status of Formoder

Abstract

Formoder, short for Formant-Moment Coder, is a system which utilizes slowly varying parameters and discrete linguistic features extracted from the speech spectrum for speech band-width compression. Formoder offers a different approach than Vocoder for the approximation of the speech spectrum by using FM as well as AM parameters. In addition, the use of certain linguistic features limits the dynamic ranges needed in the analyzer and synthesizer components. The system falls short of the ideal representation of a time varying dynamic model of the speech mechanism, but it holds promise for an improvement in compression ratio over that of Vocoder. This is perhaps the reason for continued study of essentially similar systems in various laboratories. This paper is intended to discuss further the above-mentioned points and will describe the present status of Formoder together with system evaluation and articulation tests. In a typical operation of the system using two formants and one moment, articulation tests show the Harvard PB word lists score over 40% and sentence score over 80%. [The research in this paper has been made possible through support and sponsorship extended by the Electronics Research Directorate of the Air Force Cambridge Research Center, under Contract AF19(604)-1039, Item I, and AF19 (604)-2198.]