NRL, Code 7131, 4555 Overlook Ave. SW, Washington, DC 20375-5000
Near periodic arrays of discontinuities have been predicted to have a significant impact on the acoustic properties of elastic structures. Recent experimental results obtained at the Naval Research Laboratory have demonstrated the importance of the multiple scattering of flexural waves on the acoustic far field, but the surface propagation characteristics of such structures are still uncertain. Near-field pressure measurements of the response of an irregularly ribbed cylindrical shell to a point drive have now been performed. Using near-field acoustic holography (NAH), the surface velocity field of the structure is reconstructed, and further data analysis, modal and wave-number decomposition, is performed. The dispersion relations and the associated apparent damping factors for the propagating waves on the structure are hence experimentally determined. These results and interpretation of the data will be presented.