**Abstract:**

Regularly ribbed plate constructions are common in marine, aircraft, and other structures, and their vibrational response has been a subject of many theoretical studies. Most studies have been concerned with propagating waves in one-dimensional structures. In order to understand two-dimensional structural vibration, radiation, and near fields due to point-force excitation, it is helpful to study the distribution of surface velocity in two-dimensional wave-number space. This presentation is intended to clarify the physics of the complex response of such a periodic structure. An exact solution for the surface velocity response of a fluid-loaded ribbed plate subjected to a point-force load is solved for the distribution in wave number of the surface velocity. The result is graphically presented as a ``movie'' of color images of the velocity distribution where time is proportional to frequency. Overlaid indicators delineating the acoustic response region, Bloch-wave dispersion contours, and rib response filtering actions help to clarify the complex response patterns and their interactions.

ASA 133rd meeting - Penn State, June 1997