ABSTRACT
In this chapter, the authors demonstrate applications of the positive distributions to study acoustic scattering and acoustic transients. Comparisons to spectrograms are provided to highlight advantages provided by the positive time–frequency distributions (TFDs). TFDs are particularly useful in analyzing a signal when the spectral properties of a signal are changing in time. The chapter provides the examples of a positive TFD of the acoustic scattering response from an underwater cylindrical shell, and of a transient signal from an underwater vehicle, with comparison to the results obtained using spectrograms. D. Groutage and D. Bennink have developed a method of moments for deriving features from density functions derived from a singular value decomposition of energy density TFDs. The transformed singular value decomposition method has been applied to classification of acoustic transients signals collected on sonar systems. Dispersion is yet another important mechanism that induces changing frequencies in a signal as it propagates, particularly in acoustics.
