The active control of vibro-acoustic response using sound pressure feedback is numerically studied. An output feedback approach based on sound pressure measurement for modal pole placement is proposed. The control performance is evaluated for the case of a baffled plate. The finite element method and the Rayleigh integral are used to model the structural vibration and sound radiation. Measures of observability of a mode in pressure outputs and the effect of time delay in the pressure feedback loop are discussed. Numerical results show that the chosen poles may be assigned to predetermined values by the active control with complex gains. It is also demonstrated that the pressure feedback control may make a very large reduction in acoustic radiation and structural vibration of the controlled modes in a wide frequency band when using constant gain at a lower frequency.

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The effects of attachments on the dynamics of a master structure are of fundamental significance. In this study, the changes in the vibro-acoustic behavior of a fluid-loaded plate due to variations in lumped mass attachments are examined. The finite element for modeling the structure with lumped mass attachments is coupled with the Rayleigh integral for the acoustic fluid to solve the structure–fluid interaction problem and to obtain the response of the coupled system. The changes in the modal parameters due to the variations in attachments are determining from a model reduction method. The Monte Carlo simulation is used for the uncertainty analysis of the vibro-acoustic behavior. Both the mean and the standard deviation of the changes attributable to the attachments are discussed. A baffled plate with water loading/air loading is involved in the study. The numerical results show that the effects and the changes-in-impedance on the master plate due to the attachments vary with the frequency spectrum.

Experiments involving a sonar platform with a sound absorption wedge were carried out for the purpose of obtaining the low frequency acoustic characteristics. Acoustic characteristics of a sonar platform model with a sound absorption wedge were measured, and the effects of different wedge laid areas on platform acoustic characteristic were tested. Vibration acceleration and self-noise caused by model vibration were measured in four conditions: 0%, 36%, 60%, and 100% of wedge laid area when the sonar platform was under a single frequency excitation force. An experiment was performed to validate a corresponding numerical calculation. The numerical vibration characteristics of platform area were calculated by the finite element method, and self-noise caused by the vibration in it was predicted by an experiential formula. The conclusions prove that the numerical calculation method can partially replace the experimental process for obtaining vibration and sound characteristics.

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