Active control of interior noise using piezoceramic actuators.

Abstract

Active control of aircraft interior noise has recently received increased emphasis as an effective, lightweight noise control approach. Flight tests have demonstrated 10 to 15 dB of noise reduction using distributions of interior acoustic sources. However, to achieve control over the first three to five blade passage harmonics, actuator numbers ranging from 16 to 32 or more have been used. Additionally, the optimum distribution of actuators changes between those frequencies associated with the first one or two harmonics and the higher harmonics. Recent work at NASA Langley has investigated the use of piezoceramic patches bonded to the shell surface of a large-scale composite fuselage model. These were used as force actuators in an active control system where the interior acoustic pressure was minimized using a least-means-squares algorithm. Results show an 8- to 15-dB global noise reduction for a variety of test conditions. The results are compared for different actuator numbers, locations, and excitation conditions. Generally, it was found that in-plane force excitation is more effective for controlling the required low-order azimuthal modes. Also, frame-mounted actuators were found to be effective under certain conditions. Finally, the implementation of the control system and the transducer arrangement will be related to the mechanisms controlling the noise transmission and radiation coupling.