Joint using the finite element method and acoustic radiation modal method to solve the sound power structure sheet radiation, the structure radiation sound power about the design variable sensitivity was analyzed. In the structure vibration link, surface vibration velocity was obtained using the finite element method; in the sound radiation link, the sound field information about radiation of surface vibration can be obtained by expansions of the acoustic radiation modes. For the radiation of a stiffened panel, sound power sensitivity with respect to design variable was analyzed, and the results showed that the sound power was reduced by using stiffeners when the excitation frequency was far from the natural frequency of the body, but it had negative influence and was useless by using stiffeners when the natural frequency was close to the excitation frequency.

The location of optimization of piezoelectric actuator based on the theory of radiation modes in the active control decoupling is studied. Previous researches have proposed that as long as four groups of actuators are arranged symmetrically, active control decoupling based on radiation modes can be achieved. Since there are many symmetrical layouts for the four groups of actuators, it is worth studying which layout is the best. In this paper, based on the object of minimizing the input control power, the locations of the four groups of piezoelectric actuators are optimized.

According to the features of radiation modes, four groups of forces are presented. Based on this arrangement method, four independent controllers are designed by using theΗ∞algorithm. And the controllers can be uesd to control the first four acoustic radiation adjoint coefficients to minimize acoustic power. The method converts the complicated control system of four inputs/outputs into four simple independent systems of single input/output, thus each group of controlling forces can independently control the corresponding adjoint coefficient. The simulation result indicates that this method can realize decoupling control and decrease acoustic power obviously.

The sound power sensitivity of viscoelastic damping plates is analyzed by using acoustic radiation modes. Two cases of plates, one with damping layer and the other with viscoelastic beams, are considered and compared. The influence of the thickness of the damping layer on the sound power sensitivity is found. The numerical examples show that it is effective for control of the sound power of plates by increasing suitably the thickness of the damping layer and locating reasonably the viscoelastic beams.