ASA 125th Meeting Ottawa 1993 May

5aSA8. Scattering from a finite width panel with attached internal resonances in an infinite baffle.

Daniel A. Russell

Judith L. Rochat

Allan D. Pierce

Victor W. Sparrow

Grad. Prog. in Acoust., Penn State Univ., 117 Appl. Sci. Bldg., University Park, PA 16802

Recent research has shown that the vibration response of a finite panel in an infinite baffle may be strongly affected by attaching structures which have internal resonances. In another study ongoing at Penn State, it has been demonstrated that the mass of a fuzzy attachment has a significant effect on the response of a system to an incident acoustic plane wave. In the present research a formalism is developed for predicting the acoustic scattering from such panels with attached masses. A plane wave is incident on a panel, finite in one direction and infinite in the other, with light fluid loading assumed. The backscattering cross section and target strength are calculated for the panel alone. Attachments, treated as lumped element masses, are then added to the panel producing internal resonances of the system. In this paper, the attachments are assumed as well known, they are not fuzzy. The backscattering and target strength are calculated and compared to those of the panel without attachments. An effective scattering cross-section length then may be determined. [Work supported by ONR.]