Central Inst. for the Deaf, 818 S. Euclid, St. Louis, MO 63110
Using the autocorrelation method, LPC error signals were computed as differences between the original waves and the predicted waves at each time instant. Analyses of synthesized and human vowel sounds show that the shapes and spectral contents of the instantaneous error signals are almost identical with those of the voice source for synthesized vowel sounds, and that the instants of glottal closure are well defined as maximally negative peaks in the error signals for both kinds of vowel sounds. Time integration of error signals was also performed. For male voices the shapes of integrated and instantaneous error signals are found to be very similar with those of EGG and differentiated EGG signals, respectively. This result supports the possibility that open and closed phases of the vocal folds within each glottal cycle can be determined from such LPC error signals. It was also found that automatic detection of valleys (or peaks) in the integrated error signal may be a robust pitch estimation method for voiced speech segments including synthetic diplophonic sounds. These and other results suggest that these simple LPC error analyses may provide significant information about the voice source.