Spectral analysis of glottal flow models

Abstract

An analysis of the effects of time-domain characteristics of glottal waveforms in the spectral domain is presented. Studies have shown that the relative difference in amplitude of the first two harmonics of the inverse-filtered voice waveform (H1*−H2*) can be used to predict the value of the open quotient in certain situations [J. Sundberg, M. Andersson, and C. Hultqvist, J. Acoust. Soc. Am. 105, 1965–1971 (1999)]. However, recent experiments have shown that glottal waveform asymmetry is an additional factor that will affect the relationship between the harmonics and open quotient. This work is aimed at establishing a method in which both the open quotient and a glottal asymmetry coefficient can be reliably determined based on the characteristics of the first two harmonics. By deriving analytic formulas for the spectra of two glottal flow models (LF, R++), it is shown that a measure of the relative phase difference of the first two harmonics as well as the amplitude difference can be used in order to determine these perceptually important time-domain parameters of the glottal waveform. A theoretical analysis as well as experimental results are presented.