Active Control of Noise in a Three-Dimensional Enclosure

Abstract of Master's Thesis (December 1995)

In this thesis, which is motivated by recent developments in active structures, analytical and experimental investigations into the active control of noise in a three-dimensional enclosure are conducted. Five walls of the enclosure are constructed from acrylic material. The other wall, which serves as a flexible boundary, is constructed from either aluminum or composite material. Active control is realized by using Lead Zirconate Titanate (PZT) piezoceramic actuators bonded to the flexible panel. Condenser microphones are used as sensors for interior and exterior noise measurements. In the experiments, noise generated by an external speaker is transmitted into the enclosure through the flexible wall. Control of this noise is attempted at a discrete location in the enclosure or at a set of locations in the enclosure. Four cases are considered in the experiments: a) a simply supported aluminum panel, b) a clamped aluminum panel, c) a clamped graphite/epoxy panel, and d) a clamped Kevlar panel. For tonal disturbances, results obtained from an analytical model are compared with the corresponding experimental results obtained for the aluminum panels. The analytical and experimental results compare well and are indicative of the strong possibilities for carrying out active noise control in three-dimensional enclosures such as rotorcraft cabins.