Linear prediction on a warped frequency scale [speech processing]

An ordinary predictor and a frequency warped predictor are compared in an ADPCM (adaptive differential pulse code modulation) system. The experimental results show that for an unwarped predictor of order ten, the order of the warped predictor can be reduced by two for the same speech quality. The audible differences between the normal and the warped predictors are very small, so the statements of the test subjects are widely spread. The measured noise of the system with the warped predictor is about 2 dB higher than the normal predictor, but it has lower audible noise. However, the plosives (p, t, etc.) are more blurred. The measured SNR was taken from the difference of the signals before the preemphasis filter and behind the deemphasis filter at the end of the system. Comparing the computing time needed to obtain the predictor coefficients, the difference between the normal and the warped predictor is negligible