The mechanism of sound transmission control in terms of structural and radiation modes

The dynamic response of a clamped rectangular plate subjected to plane wave incidence and piezomoment actuation has been derived in our previous research. The result benefits the comparison of acoustic power transmitted through the plate with and without control. The acoustic power is represented in terms of the amplitudes of the structure modal velocities and the velocities of an array of elemental radiators on the plate surface. It was found that the transmitted acoustic power due to the vibration of one structural mode or element depends on the vibration of other structural modes or elements; however, the radiation modes contribute to the transmitted acoustic power independent of other radiation modes. Three control strategies, viz. volume velocity cancellation, minimization of the transmitted sound power, and minimization of the vibration energy of the plate, are employed. The control mechanism in terms of structural and radiation modes is thoroughly discussed. The control is found to be much more effective when it is applied to the high-radiation-efficiency modes than to other modes. ©1999 Publication Board, Japanese Journal of Applied Physics.