78. A speech analysis and synthesis system as defined in claim 77 wherein said means for analyzing said frame of speech data with a Cepstrum generator 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 signal; and means for adding said weighting signal to said Cepstrum signal along said dimension in the direction of the abscissa thereof to generate a weighted Cepstrum signal.
77. A speech analysis and synthesis system as defined in claim 75 wherein said means for analyzing said frame of speech data to produce a digital voiced/unvoiced decision parameter further includes; means for comparing an error signal generated by said linear prediction coefficient generator 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.