Active Structural Acoustic Control with Adaptive Structures Including Wavenumber Considerations

The structural acoustic control of a baffled simply supported plate was modeled analytically to determine the feasibility of using the model to design shaped sen sors. Results from the analytical study were compared to those obtained in experiments previously conducted that implemented either microphones or polyvinylidene fluoride (PVDF) strips as error sensors. Since the experimental data was subjected to a 40 dB dynamic range (due to A/D of controller as well as noise floor of instrumentation), the theoretical control approach was modified such that the analytical model would be limited to the same dynamic range. To evaluate the success of the structural acoustic control, radiated sound pressure was measured or computed in an arc perpendicular to the plane of the plate. Analytical predictions for sound radiation before and after control correlated well with the data obtained in the experimental investigation. In an effort to explain the physical mechanism of control, the k-transform of the structural response was computed. Results from this analysis indicate that structural acoustic control is achieved when the supersonic wavenumber components are reduced. Based on this conclusion, the possibil ity of implementing a cost function in the k-domain was investigated, and results suggest that sensors shaped for observing only the supersonic wavenumber components of the 2-D k-transform would yield a minimization of the acoustic response of the structure.