Active acoustic control of a rocket fairing using spatially weighted transducer arrays

A preliminary study, including experimental results for a novel active acou stic control approach to reduce the low-frequency modal response in a rocke t fairing, is presented. The control method uses spatially weighted transdu cer arrays with Hz feedback control laws to attenuate globally the targeted acoustic modes. The nature of the fairing acoustic problem is described, t he theory of the control approach is discussed, and important feasibility i ssues regarding the actual implementation of the control method are present ed. Several controllers were implemented on a full-scale composite model of a small rocket fairing, The results demonstrate that the controller was ab le to reduce the response of the low-frequency modes by 6-12 dB with very l ittle spillover. In addition, a spatially averaged reduction of the acousti c response of the fairing interior in excess of 3 dB over the 20-200-Hz ban dwidth was demonstrated. The feasibility studies indicate that limitations on actuator power and volumetric displacement under actual launch condition s are not necessarily prohibitive, but may be satisfied with continued deve lopment of actuator technology and placement optimization.