Communications Project

Document Type:Master's Thesis
Name:Brody Dylan Johnson
Title:Control of broadband acoustic radiation from structures using a piezoelectric double-amplifier active-skin
Degree:Master of Science
Department:Mechanical Engineering
Committee Chair: Chris R. Fuller
Committee\ Members:
Keywords:acoustics, broadband, active, skin, control
Date of defense:July 23, 1997
Availability:Release the entire work for Virginia Tech access only.
After one year release worldwide only with written permission of the student and the advisory committee chair.


In this work, the potential of an active-skin is demonstrated for the reduction of broadband acoustic radiation from a vibrating structure. A simplified representation of the active-skin, employing acoustic monopoles as secondary sources, is explored as a precursor to the more complicated analyses of the device. Many design issues are addressed at this stage, taking advantage of the simplicity of this model. Numerical Methods, such as the Finite Element Method (FEM), are employed in the development of both structural and acoustic models for the active-skin. These modeling techniques are also employed for the primary structure, a simply-supported steel plate. The obtained models of the plate are validated using both theoretical and experimental comparisons. Experimental results are also used to verify the structural and acoustic models of the active-skin. Integration of these models into the control simulation provides a methodology for investigating the control characteristics of the active-skin. Two different skin configurations are investigated. The first employs the active-skin as a partial covering of a steel plate, while in the second configuration the active-skin completely covers a clamped aluminum plate. In each case, experimental results are presented, in which microphones are used as error sensors, for validation of the analytical active-skin model. The model is then used to investigate the effect of Structural Acoustic Sensing (SAS) on the control performance as an alternative to microphone error sensing. The adaptive feedforward Filtered-x Least-Mean-Square (LMS) algorithm is employed for both analytical and experimental control simulations showing the utility of such an active-skin in the control of structure-borne sound. A summary of the analytical and experimental findings is given and conclusions are drawn from these findings regarding the potential for the active-skin in the broadband attenuation of structurally radiated sound.

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