Showing papers on "Cepstrum published in 1968"
TL;DR: Several methods of fundamental frequency and period measurement, based on these concepts, are described and the results of computer simulations and analog instrumentations indicate that these new methods compare favorably with, and in some cases exceed, the capabilities of cepstrum analysis.
Abstract: The fundamental frequency of a periodic signal whose fundamental component is not available for measurement can be determined by measuring the frequencies of its higher harmonic components and computing the largest common divider of these frequencies. Similarly, the fundamental period can be determined by measuring the periods of individual harmonics and finding their smallest common multiple. Several methods of fundamental frequency and period measurement, based on these concepts, are described in this paper. The results of computer simulations and analog instrumentations indicate that these new methods. at a considerable reduction in complexity, compare favorably with, and in some cases exceed, the capabilities of cepstrum analysis.
312 citations
TL;DR: Experimental tests have been made on a computer-simulated channel vocoder to see whether pitch perturbation can be effectively simulated by partially replacing voiced excitation by random noise, in appropriate frequency-time portions and shows that partial devoicing of the high-frequency ranges definitely improves speech quality.
Abstract: Aperiodicity in voiced segments of speech may be ascribed to different causes. The magnitude of pitch perturbation is different in different spectral ranges of the signal. To see whether pitch perturbation can be effectively simulated by partially replacing voiced excitation by random noise, in appropriate frequency-time portions, experimental tests have been made on a computer-simulated channel vocoder. The buzz-hiss decision was made separately for three different frequency portions of the signal. The cepstrum technique was used for pitch detection, and separate buzz-hiss switching decisions were made at the synthesizer for each frequency portion. The switching thresholds were controlled, and deliberately "devoiced" versions were compared with regular vocoded speech. The fundamental frequency was determined by the lowband cepstrum. The result shows that partial devoicing of the high-frequency ranges definitely improves speech quality. Further, a comparatively large amount of devoicing is perceptually tolerable.
55 citations