Analysis/synthesis and modification of the speech aperiodic component

The general framework of this paper is speech analysis and synthesis. The speech signal may be separated into two components: (1) a periodic component (which includes the quasi-periodic or voiced sounds produced by regular vocal cord vibrations); (2) an aperiodic component (which includes the non-periodic part of voiced sounds (e.g. fricative noise in /v/) or sound emitted without any vocal cord vibration (e.g. unvoiced fricatives, or plosives)). This work is intended to contribute to a precise modelling of this second component and particularly of modulated noises. Firstly, a synthesis method, inspired by the "shot noise effect", is introduced. This technique uses random point processes which define the times of arrival of spectral events (represented by Formant Wave Form (FWF)). Based on the theoretical framework provided by the Rice representation and the random modulation theory, an analysis/synthesis scheme is proposed. Perception tests show that this method allows to synthesize very natural speech signals. The representation proposed also brings new types of voice quality modifications (time scaling, vocal effort, breathiness of a voice, etc.).