Active control by using optical sensors on the acoustic radiation from square plates

This study is reported of an optical approach to reduce the acoustic radiation from some uniformly square plates of different sizes. The content of this study includes the dynamical analysis of uniform plates, the theoretical consideration dealing with both the optical-error path and neural network control system, and the laboratory demonstration on the acoustic-radiation reduction from plates by using optical approach. Results of dynamical analysis on three different plates obviously reveal low odd–odd modes such as (1, 3) and (3, 3) mode must respond to the most acoustic radiation from plates. Laboratory demonstration claims that much more reduction of acoustic radiation from plates within greater frequency range can be reached when using an optical-error path to replace acoustic-error path. The corresponding experimental results obviously show that the greater control effectiveness on (3, 3) mode for smaller plate, single frequency, the greater effectiveness by 26 dB of acoustic radiation reduction for single point control than that for multi points control. Regarding to the double frequencies, the acoustic attenuation by 14.6 dB for compose of (3, 3) and (3, 4) in 60 cm plate are obtained.