Voiced/unvoiced band-switching system for transmission of 6 kHz speech over 3.4 kHz telephone channels

A voiced/unvoiced band switching system is described for the transmission of wide bandwidth speech (here 300to 6000 Hz) over commercial telephone channels. Timewaveforms and spectrograms are presented to demonstrate that the 6 kHz speech can be compressed into a 3-4 kHz telephone channel and yield improved speech quality at the receiver compared to current telephone quality speech. Informal listening experiences confirm these results. The system is conceptually simple and inexpensive to implement.