A time warper for speech signals

A parabolic time warper designed to enhance the stationarity of voiced speech segments, is presented. It is shown how, for a harmonic signal segment, the parabolic time warping function can remove the part of the frequency variation which progresses linearly with time, without changing the time duration of that segment. In the actual implementation of the time warping system, the linear part of the pitch frequency variation in a segment is removed on the basis of maximization of the pitch-related autocorrelation peak of the warped signal. As a by-product, the time warper yields a very reliable pitch estimation. An example on real speech is discussed.