Complex Wavelet Based Envelope Analysis for Analytic Spectro-Temporal Signal Processing
Jean-Marc Luneau, Lebrun, Jerome, Jensen, Søren Holdt · 2008
A new class of spectro-temporal signal transforms often called Modulation Transforms has recently been introduced. They add a new dimension to the classical time/frequency representations, namely the modulation frequency. Very efficient in many applications, especially at the analysis level, these transforms show however their limits when it comes to signal processing in the transform domain. The modulation spectrum is commonly obtained by spectral analysis of the sole temporal envelope of the sub-band signals. Simple filtering in this domain has been shown to create serious distortions. We detail here some of the reasons for this and propose the use of a complex wavelet transform as a more appropriate envelope and phase processing tool. By working in an alternative transform domain coined as Modulation Sub-bands, this transform shows very encouraging denoising capabilities and suggests new approaches for joint spectro-temporal analytic signal processing in general. This work was supported by the European Union via a Marie Curie Fellowship (EST-SIGNAL program http://est-signal.i3s.unice.fr) under contract No MEST-CT-2005-021175.)