The importance of phase information in the perceptual quality of the speech signals is studied in this paper. Many speech synthesisers do not use the original phase information of the signals assuming their contribution is almost inaudible. The Relative Phase Shift, (RPS) representation of the phases allows straightforward phase structure analysis, manipulation and resynthesis, and we use these features to do a comparative evaluation of some phase modifications usually found in speech models. The final intention of this study is to get an answer to the question of whether phases deserve elaborate models to get high quality synthetic speech, or their subtle effects justify overlooking them.

Index Terms: phase perception, RPS, speech synthesis