Abstract
The studies concerning the information contained in S. S. B. -clipping of speech has been reported by the authours, in which the information of speech is preserved best by procedure of band-division in each formant region, and the envelope restoration of S. S. B. signal when the phase redundancy can be ignored were also stated. The band-compression system, i. e. Formac, presented in this paper is a system in which information source is an S. S. B. -clipping signal of speech having equivallent spectrum distribution of phase modulation, and the time variation of instantaneous frequency of this signal is extracted in each formant region. Furthermore, this principle has been compared with that of the Vocoder system. From the results of the study, Formac system has been developed which such good results as over 80 % syllable articulation with only one-third of the ordinary speech bandwidth were attained.
