Communication system capable of improving a speech quality by classifying speech signals

Abstract From the Canadian patent

In an encoder device which is for use in combination with a decoder device in a communication system and which encodes a sequence of digital speech signals into a sequence of output signals by the use of a spectrum parameter and a pitch parameter a subsidiary, parameter of the digital speech signals is detected and monitored by a monitoring circuit to classify the digital speech signals into a voiced sound and a voiceless sound or into vocality, nasal fricative, and, explosive at every frame. On detection of the voiced sound or the vocality, a predetermined number of excitation pulses are calculated only during a representative subframe after dividing each frame into a plurality of …