Bandwidth reduction of speech signals using feedback residue compression

Traditionally, bandwidth compression techniques for speech signals have consisted of two classes - time domain techniques such as delta modulators which operate at high bit rates (16 KBPS to 40 KBPS) or spectral domain techniques such as vocoders which operate at very low bit rates (2.4 KBPS to 4.8 KBPS). Concomitant with this division has been the choice between natural sounding systems which preserve the speech signal in spite of background noise and artificial sounding systems which are highly susceptible to errors induced by background noise in the speaker´s environment.