Identification of Complex Dispersion Relations in Cylindrical, Foam-Lined Ducts

Complex dispersion relations in a cylindrical, foam-lined duct were successfully identified by using an iterative Prony series method. Techniques for using the iterative procedure successfully are described in detail, particularly with regard to model order selection and the identification of parameter starting values. It is shown that modal wave speeds and spatial attenuations per wavelength can be derived from the complex dispersion relations obtained using the iterative procedure. In addition, a finite element simulation is shown to well represent corresponding experimental measurement in terms of modal wave speeds and spatial attenuations.