P. R. Stepanishen
Dept. of Ocean Eng., Univ. of Rhode Island, Kingston, RI 02881
Q. Huynh T. Greene
Naval Undersea Warfare Ctr., Newport, RI 02841
Linear and quadratic time-frequency transforms are used to investigate and characterize transient signals from several wave propagation problems in structural acoustics. The transforms include: the short-time spectrum, Wigner type representations, and wavelet methods. Advantages and disadvantages of the various representations within the present context are presented. Particular emphasis is placed on using the wavelet packet method of Coifman to analyze and characterize complex transient signals from various structural-acoustic transmission paths with dispersive characteristics. Adaptive procedures are used to determine optimal time-frequency localization by using the best basis functions for the class of dispersive signals of interest. Various features and parameter extraction methods based on the local maxima of the wavelet transform at each scale are presented for several complex transient dispersive signals. [Work supported by ONR.]