Methods of vibration field control using actuator array for improving the panel speaker sound

The panel speaker occupies a small volume, so it has significant merit potential in application to modern machines and devices in the age of Internet-of-Things. However, the severe fluctuation in the radiated sound spectrum due to the multi-modal vibration behaviour of finite panels has been an inherent problem. The application of damping can reduce the resonance effect, but the frequency range is limited to a narrow band. Actively, the actuator array can control the vibration field of the plate. The vibration rendering for the desired vibration pattern or the elimination of some modes is possible by controlling the modal contribution or the boundary impedance in the frequency range of interest. An inverse formulation, which is analogous to the acoustic field rendering problems, should be solved to determine the actuators' control gain for achieving the desired response. In this presentation, several methods for active array control of the vibration field for panel speakers are compared: vibration field rendering using the modal approach, direct inverse technique fulfilling the desired sound radiation, boundary impedance control using traveling wave, and sparse actuator array allocation method. Their merits and demerits are discussed regarding the future potential in various applications.