Psychoacoustically based scalar quantization of the LPC poles

The most straightforward way to incorporate knowledge of formant perception in LPC scalar quantization is by quantizing the LPC poles. The authors measured directly the perceptual sensitivity to changes in the poles during continuous speech, and used these data in the design of a scalar quantization scheme. The average pole-frequency just noticeable difference (JND) was found to strongly decrease with increasing formant bandwidth, and to depend to a lesser degree on the frequency. A considerable coding efficiency was achieved by utilizing the JND data and the measured distribution ranges of the pole frequencies. A 30 bits per frame quantization produced similar speech quality as that obtained with a standard 41 bits quantization of the reflection coefficients