Analysis and perception of spectral 1/f characteristics of amplitude and period fluctuations in normal sustained vowels.

Abstract

Two kinds of fluctuations are always observed in the steady parts of normal sustained vowels. One is amplitude fluctuation, defined as the cyclic changes of maximum peak amplitudes. The other is period fluctuation, defined as the cyclic changes of pitch periods. The primary purpose of this paper is to present quantitative descriptions of amplitude and period sequences obtained from normal sustained vowels. These fluctuation sequences consisted of maximum peak amplitudes or pitch periods extracted successively from 512 consecutive pitch periods in the steady part. Results of the frequency analysis indicated that their frequency characteristics seemed to be subject to the spectral 1/f power law. In order to investigate the possibility that the frequency characteristics of the fluctuation sequences influence the voice quality of sustained vowels, psychoacoustic experiments were conducted. Amplitude and period sequences evaluated in the experiments were spectral 1/f0 (white noise), 1/f, 1/f2, and 1/f3 sequences, respectively. The experimental results indicated that the subjective voice quality of synthesized sustained vowels could reflect the differences in the frequency characteristics of the fluctuation sequences.