Linear predictive method for improved spectral modeling of lower frequencies of speech with small prediction orders

An all-pole modeling technique, Linear Prediction with Low-frequency Emphasis (LPLE), which emphasizes the lower frequency range of the input signal, is presented. The method is based on first interpreting conventional linear predictive (LP) analyses of successive prediction orders with parallel structures using the concept of symmetric linear prediction. In these implementations, symmetric linear prediction is preceded by simple pre-filters, which are of either low or high frequency characteristics. Combining those symmetric linear predictors that are not preceded by high-frequency pre-filters yields the proposed LPLE predictor. It is proved that the all-pole filters computed by LPLE are always stable. The results achieved with vowels show that the proposed method is well-suited for those applications, where low-order all-pole models with improved modeling of the lowest formants, are needed.