Approximation method for time-domain simulation of the lossy vocal tract and evaluation of frequency-dependent losses during glottal source flow

摘要

In this paper, we propose a new approximation method for realizing a digital filter model for the lossy vocal tract with a view to evaluating the effect of the interaction between the vocal tract and the subglottal system, which has a frequency-dependent factor in the vocal-tract analog. In our approximation, for the propagation factor we compose an analog filter using the combination of a pair of poles and zeros with a different real part and the same imaginary part, and carry out a transfer from the s domain to the z domain using the delta transform. For the reflection coefficient we compose a Finite Impulse Response (FIR) filter of 511-order by Fast Fourier Transform (FFT) computation. It is known that the ripple component can be observed in the glottal source flow as the effect of the interaction. Here we show that this ripple component is reduced and the duration of the glottal open phase is increased as effects of the frequency-dependent characteristics of the loss.