Control of sound radiation with adaptive structures

Results are reported from an experimental study tracing active control of sound radiation from a vibrating simply supported rectangular plate excited by a steady-state harmonic point force disturbance. A variety of test cases for controlling sound radiation due to a disturbance both on and off structural resonance are examined. Control structural inputs are achieved by three piezoceramic actuators bonded to the surface of the plate. The control approach is based on a Filtered-X version of the adaptive LMS algorithm. Piezoceramic elements are found to provide an efficient method for modification of a structural response to attenuate sound radiation. In many cases, polyvinylidene fluoride piezoelectric distributed sensors are as effective as microphones in providing the error information necessary to reduce the far-field sound radiation from the structure. The LMS algorithm is shown to be an effective narrowband controller, which, in contrast to feedback approaches, requires no exact system modeling.