Abstract: A system and method for detecting the presence of useful speech information in telephone voice channels capable of containing noise as well as such useful speech information for optimizing the telephone transmission of such speech information. Two segments of the envelope of a given voice channel are compared against each other over two different time domains in order to determine if a predetermined magnitude of difference exists between these envelopes. The presence of such magnitude of difference is indicative of the presence of such useful speech information in the voice channel thereby enabling transmission thereof by the system, whereas the absence of such magnitude of difference is indicative of the presence of solely noise thereby preventing the transmission thereof by the system.

Abstract: A pulse-code modulation transmission system having reduced redundancy and high transmission quality utilizes a variable companding law and variable number of bits per sample both of which vary in accordance with the type and/or short-time volume of the signal associated with a particular talker as well as with the type and/or short-time volume of all of the signals associated with all of the talkers handled by the transmission system. The system utilizes the envelope or modulating signal for the speech signal to provide a companding law which varies as the talker varies and, for a particular talker, as the short-time volume of that talker varies, so that redundancy can be reduced without impairing transmission quality. This companding law adapts itself to the vowels, consonants and syllables of the word in accordance with their volume in order to optimize the signal to quantizing noise ratio.