Noise control of structures with dipole acoustic cell devices, an analytical study

Abstract

A new passive surface treatment has been developed to attenuate low frequency radiated noise from large structural surfaces. The acoustic treatment consists of an array of weak radiating cells that covers the structure’s surface. Each cell is a mechanical device that has two surfaces. The cells are driven by the motion of the structure and designed such that the two surfaces operate nearly out-of-phase, effectively creating dipole acoustic sources. Preliminary experimental results for nine cells applied to a simply supported plate driven by a white noise input show a 10 dB of sound power reduction over a frequency range of 100–1600 Hz. An analytical model is used to gain physical insight on noise control properties of the cells-plate system. Interaction effects of the system such as mass loading, damping, and dynamic coupling of the cells and plate are also investigated. The model is also utilized in design optimization studies of the weak radiating cells for beam and plate structures subjected to broadband inputs.