The Application Of The Decoupling Of The Active Structural Acoustic Control Based On The Theory Of Radiation Modes

The theory of radiation modes is an effective method to study the problem of sound power radiated from vibrating structures.In this paper,radiation modes and its corresponding radiation efficiencies can be obtained and adjoint coefficient is defined by studying the relationship between the surface normal velocity and the surface sound pressure of vibration structure.Because of radiation modes orthogonal to one another, the sound power of each radiation modes is completely independent of one another, and the total sound power radiated from the vibration structure is the summation of the sound power of all radiation modes.The lower-order radiation modes radiate much more efficiently than the higher-order radiation modes in the low frequency range,and the sound power of the lower-order radiation modes is main contribution to the total sound power.In the system of ASAC,good effect would be achieved if we controlling the sound power of the former radiation modes.In the ASAC system,suitable arrangement of actuators can not only reduce the sound power effectively,but also make the control easily.In the system of ASAC which based on the radiation modes,fine effect of sound reduction would be achieved if we arrange the control actuators take full account of the radiation modes shapes.In this paper,four group actuators are presented in according to the characteristics of the first four radiation mode shapes and make full use of the merits of lightweight and flexibility of the piezoactuators,when studying the vibration responses of the four group actuators discovered that the vibration responses of the four group actuators coincide with the symmetric fashions of the first four radiation modes respectively,and each group of actuators only excites the vibration of the special radiation mode.Applying the four group actuators which only excite the vibration of the special radiation mode to the ASAC system,theoretical analysis and numerical calculation demonstrate that the four group actuators are control independently and can make the decoupling of the control process.While controlling the sound powers of the first four radiation modes,these actuators can convert the complicated control system of multiple input/output into several simple and independent systems of single input/output.