Active structural modal control for sound reduction in an enclosure: Experimental verification

Abstract

Sound radiation from a vibrating enclosure into an enclosed space can be actively reduced using sensors and actuators attached to the enclosure. However, the sound cannot be effectively reduced by merely minimizing the structural vibration, as the levels of the vibration and the radiated sound are not proportional to each other. Moreover, reducing the sound using the actuators can lead to increased vibration. In an earlier work by the authors, a control system was theoretically developed to achieve two goals simultaneously. The primary objective was to effectively reduce the sound in the enclosure, and the secondary objective was to prevent the vibration of the enclosure from increasing. In this study, an experiment is conducted to verify this theory. The control system design begins with identifying the most acoustically contributive structural modes, by theoretically calculating the structural modal acoustic potential energies. Once the most acoustically contributive structural modes are identified, sensors and actuators are configured to preferentially measure and control these structural modes. The control strategy is based on the idea that the most acoustically contributive structural modes should be suppressed by the actuators, whereas the other structural modes should not be affected by the actuators. The experimental results indicate that sound in the enclosure can be effectively reduced and the vibration of the enclosure can be prevented from increasing.