Robust feedback control of flow-induced structural radiation of sound

A significant amount of the interior noise of aircraft and automobiles is a result of turbulent boundary layer excitation of the vehicular structure. In this investigation, the feasibility of active robust feedback control of the noise due to this type of excitation is studied. The structural sound radiation system investigated is comprised of a simply supported panel excited by turbulent flow. An analytical model of this system is developed to evaluate the robust feedback control system design strategy. The model consists of a modal description of the excitation of the plate by a turbulent boundary layer, a modal representation of the plate vibrations, and an acoustic model of the sound radiated from the plate. Parametric uncertainties of 1% variation in the natural frequencies and 5% variation in the damping ratio are considered. A frequency domain controller design approach is utilized to develop a robust controller. Performance objectives are specified which include output performance of the sound radiated by the plate and control effort constraints on the force applied to the plate by the controller. Plate acceleration feedback is used in an effort to reduce the sound-pressure level. Approximately 16 and 8 dB of sound-pressure level reduction were achieved at the first and third resonances, respectively.