### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 1aSC30. Removal of phase distortion from vowel-like signals.

**Kenton A. Shipley
**
Casey R. Winkel

P. G. Vaidya

**
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*Dept. of Mech. and Mater. Eng., Washington State Univ., Pullman, WA 99164
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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, 2370--2378
(1991)] and the other uses the complex FFT components in a manner similar to a
rigid body rotation in dynamics. These methods have been used to produce both
distortion-free and highly modulated versions from a given human vowel signal.
[sup a)]Now at Martin Marietta, Knolls Atomic Power Labs, Schenectady, NY.