Peak-and-valley impulse excited LPC voice

A voice recorder/reproducer has been implemented for the purposes of applying to public address systems and other speech communication systems. In this paper, we describe speech synthesis from a peak-and-valley impulse train generated from the transmitted baseband residual signal, and hardware implementation by using commercial digital signal processors. In the conventional Residual Excited Linear Prediction (RELP) vocoder, the full-band excitation is generated so that it has a flat spectrum. On the other hand, our system, the peak-and-valley impulse train is spectrally modified by the fourth order all-pole filter so that it has approximately the same spectral envelope as that of the original residual signal, and used as the high-band excitation. A prototype model operating in real time has been implemented by using three DSPs for speech analysis, 2 DSPs for speech synthesis, and one microprocessor for the system control. Sound quality at the bit rate below 9.6 kbits/s is equivalent to that of the 7-bit linear PCM system.