Spectral phase information is usually discarded in automatic speech recognition (ASR). The Relative Phase Shift (RPS), a novel representation of the phase information of the speech, has features which seem to be appropriate to improve the ASR recognition rate. In this paper we describe the RPS representation, discuss different ways to parameterize this information in a suitable way for the HMM modelling, and present the results of the evaluation experiments. WER improvements ranging from 12 to 22% open promising perspectives for the use of this information jointly with the classical MFCC parameterization.

Index Terms: ASR, phase spectrum, harmonic analysis