Some notes on phase in speech signals

The preservation of phase information in the analysis of speech signals is, quite properly, assuming a role of increased importance. The results of a series of experiments with transformations that destroy speech signal amplitude information but retain phase are reported. These experiments include the preservation of only the phase of a short-term Fourier representation of a signal, preservation of only the phase information of the short-term direct phase cepstrum, and preservation of only the phase of the analytic signal. All of these "phase preserving" transformations are shown to retain many important features of speech signals.