Experiments on active control of sound radiation around double-wall resonance frequency

The first part of this paper will be focused on identified modal shapes and sound power measurements of a double-wall panel in the low-frequency range around the double-wall resonance frequency. New experimental results show that for a double-wall panel with one laminated pane (asymmetric panel) around the predicted double-wall resonance frequency, there exist three natural frequencies, respectively three modes. One of these modes is highly complex and the other two are real. It is characteristic that at one of these real modes both planes of the panel move exactly in phase and at the second they move precisely out of phase. The second part of the paper will be focused on the design of control system to minimize the radiated sound power from the double-wall panel and efficiency of the proposed control. The radiation efficiency for each of the identified modes was estimated with goal to define the optimal position for the piezoactuators used to minimize the radiated sound power around the double-wall resonance frequency. Different control schemes will be presented. The efficiency of proposed control schemes will be compared and illustrated by means of laser scanned vibratory patterns of the panel.