A general analysis of the active control of sound radiation from a baffled panel

Previous theoretical investigations of active means to control sound radiation from a vibrating panel have considered only the use of either acoustic control sources or vibration (point force) control sources. As such, a general understanding of the physical mechanism employed in this noise control technique has been lost. This paper presents a general analysis of the active control of sound radiation from a simply supported, baffled panel. It considers the use of both acoustic and vibration control sources. The minimization of the total sound power output is used as a criterion for actuator placement, and minimization of the sound pressure at a point is used for error microphone placement. Analytical results for minimization of the sound pressure at a point are verified experimentally. It is shown analytically that acoustic control sources operate by altering the radiation impedance seen by the vibrating panel. Vibration control sources operate by changing the panel velocity distribution, either decreasing the amplitude of the offending panel mode, and/or altering the temporal phasing of the panel modes, thereby decreasing the effective power radiation from the panel.