Speech bandwidth reduction. (Working Paper)

The current state of the art in analog and digital speech bandwidth compression is assessed with a focus on minimizing the bandwidth of the voice signal used for mobile and other voice communication systems. If techniques exist for significantly reducing the 3 kHz bandwidth while maintaining sufficient quality, the radio frequency bandwidth can be proportionately reduced. The status of speech baseband compression is still in the laboratory stage or just emerging. None of it has been applied in any large commercial operation. Hardware implementations exist that provide reasonal intelligibility in about half the normal baseband, but the basic conclusion of this review is that current techniques for reducing speech bandwidth produce a concomitant degradation in speech quality which would not necessarily be acceptable in all cases. This basic conclusion is amplified, analyzed, and supported in the evidence presented.