Abstract: The concatenative speech synthesizer employs demi-syllable subword units to generate speech. The synthesizer is based on a source-filter model that uses source signals that correspond closely to the human glottal source and that uses filter parameters that correspond closely to the human vocal tract. Concatenation of the demi-syllable units is facilitated by two separate cross fade techniques, one applied in the time domain to the demi-syllable source signal waveforms, and one applied in the frequency domain by interpolating the corresponding filter parameters of the concatenated demi-syllables. The dual cross fade technique results in natural sounding synthesis that avoids time-domain glitches without degrading or smearing characteristic resonances in the filter domain.

Abstract: Signal frames containing background sounds in a mobile radio communication system are tested for stationarity. Consecutive measures .DELTA.E.sub.n representing spectral changes in said signals from frame to frame are formed. From these measures a second measure of the rate of spectral change are formed. Finally, it is determined whether this second measure exceeds a predetermined stationarity limit .gamma.. If this is the case the signals are considered stationary.