6. A speech analysis and synthesis system as defined in claim 5 wherein said means for analyzing said speech signals to generate a voiced/unvoiced decision parameter further includes: means for comparing an error signal generated by said linear prediction technique with predetermined upper and lower limits and generating a voiced decision parameter if said error signal is equal to or less than said lower limit and generating an unvoiced decision parameter if said error signal is equal to or greater than said upper limit.
7. A speech analysis and synthesis system as defined in claim 6 wherein said means for analyzing electrical speech signal by Cepstrum technique includes a signal conditioning system for conditioning said Cepstrum signal which has, in the direction of an ordinate axis, an amplitude dimension of said Cepstrum signal and, in the direction of the abscissa, a quantity representing time, said signal conditioning system having, means for generating a weighting signal which linearly increases in value with the dimension in the direction of the abscissa corresponding to said quantity representing time of said Cepstrum, and means for adding said weighting signal tosaid Cepstrum signal along said dimension in the direction of the abscissa thereof to generate a weighted Cepstrum signal.