Active control of coupled structural/acoustic intensities in a fluid-loaded elastic plate

In this paper, active control of structural intensity and radiated acoustic power in a coupled structure-fluid system is explored. The response of an infinite fluid-loaded plate and the resultant acoustic pressure field are calculated using a hybrid analytic/numerical approach. Two control strategics are examined: (1) the minimization of the total input power, and (2) the minimization of a weighted sum of structural intensity and the radiated acoustic power. Below coincidence, the vibration response of the plate is dominated by nondecaying waves, thus it can be reduced very efficiently by the active control strategies of minimizing the total input power or minimizing the structural intensity. Below coincidence, the acoustic radiation is caused by fast decaying structural waves thus, and active control strategies that aim to minimize the structural intensity have little impact on the radiated pressure field. Furthermore, the control strategy for minimizing the radiated acoustic power does not perform satisfactorily below coincidence since the controllers cannot be coupled to the fast decaying waves. Above coincidence, a slowly decaying structural wave dominates both the plate response and the acoustic radiation, and thus the structural intensity and the radiated acoustic power can be reduced significantly by each of the two control strategies. (C) 2000 Acoustical Society of America.