Abstract: Based on the radiation modes, it is presented an active control strategy for sound radiation from elastic structures with an example of simply supported rectangular panel. The physical characteristics and mathematical meaning of the radiation modes is analyzed. The radiation efficiency of the radiation modes falls off very rapidly with increasing modes order at low frequency. A new control strategy is developed in which by canceling the adjoint coefficient of the first k radiation modes, the sound powers of the first k radiation modes is zero theoretical. The numerical calculation is made by using point force actuators as control forces.