Evaluation of mel-LPC cepstrum in a large vocabulary continuous speech recognition

This paper presents a simple and efficient time domain technique to estimate an all-pole model on the mel-frequency scale (mel-LPC), and compares the recognition performance of the mel-LPC cepstrum with those of both the standard LPC mel-cepstrum and the MFCC (mel-frequency cepstral coefficient) through the Japanese dictation system (Julius) with 20,000 word vocabulary. First, the optimal value of the frequency warping factor is examined in terms of monosyllable accuracy. When using the optimal warping factors, the mel-LPC cepstrum attains word accuracies of 93.0% for male speakers and 93.1% for female speakers, which are 2.1% and 1.7% higher than those of the LPC mel-cepstrum, respectively. Furthermore, this performance is slightly superior to that of MFCC.