Kenton A. Shipley
Casey R. Winkel
P. G. Vaidya
Dept. of Mech. and Mater. Eng., Washington State Univ., Pullman, WA 99164
In this paper, specific types of signals are considered. To generate these
signals, we begin with x(t)=A cos[wt+(phi)(t)], where A and w are constants,
but (phi)(t) is a function of time generated by a random walk. The other step
to generate the final signal is to pass x(t) through a nonlinear filter such
that, were (phi)(t) to be constant the output would be of simple harmonics at
w, 2w, 3w, etc. However, since x(t) is nonstationary, the output signal, say
y(t), would also be nonstationary. It would be shown that human vowel signals
seem to follow this nonlinear pattern. It is of interest to remove (or modify)
the phase distortion due to the randomness of (phi)(t). This has been
accomplished by using two different methods. One uses the trans-spectral
coherence technique [P. G. Vaidya and M. J. Anderson,