The use of a non-contact acoustic excitation array for the estimation of damping in aircraft panels

This paper describes the development of a non-contact exciter, based upon a loudspeaker, for use in experimental modal analysis, and in particular for the identification of modal damping. This device is shown to be almost as versatile as traditional exciters such as electrodynamic shakers and instrumented hammers. An array of four loudspeakers is used to identify modal damping in a flat plate structure with non-uniform damping treatment, a four-bay stiffened structure, and a composite aircraft panel, using the Polyreference and Resonant Decay Method approaches. The Resonant Decay Method uses force appropriation and can potentially identify a damping coupled modal model for non-proportionally damped structures. Excellent agreement is found between the two identification methods, using both traditional excitation methods and the non-contact exciter.