AN ACTIVE CONTROL STRATEGY FOR ACHIEVING WEAK RADIATOR STRUCTURE

A general control strategy is presented for active suppression of tota l radiated sound power from harmonically excited structures based on t he measurement of their response. Using the measured response of the s tructure together with knowledge of its structural mobility, an equiva lent primary excitation force is found at discrete points along the st ructure. Using this equivalent primary force and performing a quadrati c optimization of the power radiated from the structure, a set of cont rol forces is found at selected points on the structure that results i n minimum radiated sound power. A numerical example of this strategy i s presented for a simply supported beam in a rigid baffle excited by a harmonic plane wave incident at an oblique angle. A comparison of the response of the beam with and without control forces shows a large re duction in the controlled response displacement magnitude. In addition , as the result of the action of the control forces, the magnitude of the wave number spectrum of the beam's response in the supersonic regi on is decreased substantially. The effect of the number and location o f the actuators on reductions in sound power level is also studied. Th e actuators located at the anti-nodes of structural modes within the s upersonic region together with those lcoated near boundaries are found to be the most effective in controlling the radiation of sound from a structure.