Group delay for acoustic event representation and its application for speech aperiodicity analysis

A new framework is proposed for representing acoustic events based on bandwise durations derived from a group delay function and bandwise aperiodicity indices. The goal is to provide an efficient and detailed source information for a high-quality speech manipulation system, STRAIGHT. The proposed representation enables event based processing of speech parameters and provides means to fill the gap between waveform based methods and VOCODERs in a perceptually relevant manner. Simulations using a pulse plus noise source and a time varying filter demonstrated that the proposed method provides accurate estimates of the source aperiodicity. Application of the proposed method to STRAIGHT illustrated that it enables significant reduction in storage size and improves reproduced sound quality.