Understanding the structural acoustics of stiffened shells with complexities is central to advancing the acoustic design of many aerospace and marine vehicles. Some of the mechanisms that have been studied to date include the scattering of structure-borne energy by discontinuities1–7 and the coupling of this energy into internal vibratory states leading to storage and dissipation phenomena1,8–9. Recently, we have reported the results of experiments where complex internal structure has been demonstrated to dramatically influence the scattering cross-section of fluid-loaded shells10–12 and that these effects can be predicted using spatially varying local admittance functions13. We report here for the first time measurements of the vibratory response of a ribbed fluid-loaded shell with a large number of internally attached oscillators (∼1000). Comparisons are made to the response of an identical framed shell with no internal complexity.