Robust backward adaptive formant prediction for speech coder

To improve the error performance of speech coders, an adaptation method for the backward adapted formant predictor is proposed. The filtered residual signal is used instead of the reconstructed output signal as the input to a n adaptation of the formant predictor. The performance of the filtered-resi dual driven adaption method in the noise free channel is as good as that of conventional output driven adaptation. Moreover, the new adaptation method maintains the same robustness to channel errors as residual driven adaptat ion.