Sound analysis, sound synthesis, and sound processing for audio and musical applications

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This research project aims at improving the accuracy and the adequacy of audio signal representations and modelling by benefiting from recent advances in signal processing techniques. More precisely the goal is to better address the dual nature of sound signals, which are often a mixture of temporal transients, and modulated frequency components. It will result in a better quality of sound processing, sound synthesis, and will nurture applied projects such as high-quality sound source separation or audio morphing.This project is part and parcel of the so-called analysis/synthesis approach for sound synthesis and sound processing, an often-used approach in musical applications, but also in sound design, audio coding and sound recording. The basic goal of analysis/synthesis is to conceive relevant models to represent acoustical signals by a set of temporal functions (the control parameters) that controls a synthesis structure. These temporal functions can be generated in the abstract or extracted from a pre-recorded sound during the analysis process. Re-synthesis produces a signal that sounds perceptually identical to the original sound. By modifying and substituting control parameters, this analysis/synthesis scheme can provide for very refined and precise processing of sound material. For example, it may allow one to produce a family of synthetic sound signals derived from a single original one or to carry out a morphing between two key sounds. It can also be used to make a decision on source separation by a proper sorting and grouping of temporal functions into coherent subsets.We plan to put in place a more general and higher-level description of time-varying parameters of the partials of polyphonic signals, and develop complementary analyses techniques. We also hope to provide better strategies for audio source separation that will benefit from prior knowledge of the underlying structure of sound signals, particularly as regards the phase. Finally, the extension of the analysis/synthesis approach to some classes of non-linear-systems will contribute to a more unified view of sound synthesis and sound processing and will allow for a general representation of several existing audio effects. Beyond the advance of knowledge and the training of highly qualified personnel, the expected significance in terms of applications is that a better analysis/synthesis procedure would lead to refined synthesis and processing methods. More specifically, this refinement could be decisive in applications where the separation of a few sound sources is useful, such as advanced remix for sound recording, audio restoration, coding, game industry, and movie sound effects. It would also help to design industrial applications which involve mixture of complex sounds such as 'environmental sounds' (rolling, balls, wind, water, and motor sounds).