Application of NORDEN transform to time-frequency characterization of time-varying signals

Abstract

The non-orthodox decomposition (NORDEN) transform developed by NASA [N. Huang et al., ‘‘The Empirical Mode Decomposition and the Hilbert Spectrum for Nonlinear and Nonstationary Time Series Analysis’’ (to be published)] is designed to adaptively break down a complex time-varying signal into a sum of several simple mode functions. Each single mode function can then be expressed in terms of an analytic signal whose amplitude and phase vary with time and can be displayed as a trace in a time frequency plot, the VEIN diagram, with magnitude expressed as line thickness or color coded. This methodology of signal analysis, unlike other traditional transform methods, i.e., Fourier, Wigner-Ville, and Wavelet, requires no special window, preselected kernel, or particularly selected mother wavelet and provides more detailed dynamic information about the signal under study in terms of its dominant components and their instantaneous frequency variation in the observation time. Several examples from various types of acoustic signals are examined with this algorithm to demonstrate its signal analysis capability.