Resonant response of complex shell structures

Resonances of shell structures play a prominent role in determining their a coustic characteristics. Among the most important of such characteristics a re radiated noise, scattering, and self-noise levels. The nature of the str uctural resonances, for example the number of modes within a particular fre quency band or the overall spatial dependence of the response, determines t he importance of these phenomena in various contexts and what steps may be taken to modify their acoustic impact. In the past, knowledge of the resona nt response of highly idealized systems has been used to guide the developm ent of quiet platforms. The results of a scale model investigation of the e ffects of increased complexity on the nature of the resonances of submerged shell structures are reported. Effects presented here are flexural Bloch m ode resonances, localized resonances resulting from structural irregularity , and the effects of non-axisymmetry on these phenomena. The implications o f these results on acoustic design and the development of systems is discus sed. (C) 2000 Acoustical Society of America. [S0001 -4966(00)02008-7].