The acoustic power radiated from any vibrating structure can be written as a quadratic form of the structural modal velocities. The quadratic matrix is real, symmetric, and positive definite. All of the terms with even–odd and odd–even indices are zero. The congruent transformation instead of orthonormal transformation was used to diagonalize the matrix. This method takes advantage of the good properties of the quadratic matrix more efficiently than the orthonormal transformation does. Also, the method greatly simplifies the design of the PVDF sensors, which filter the combination of appropriately weighted vibration modes, providing a specific performance index in control strategy. Based on this method, an active control system was implemented. To minimize the radiated power from a vibrating structure, a procedure to optimize the distribution of the actuators was applied to the control system.