IMAGING THE SOURCES ON A CYLINDRICAL-SHELL FROM FAR-FIELD PRESSURE MEASURED ON A SEMICIRCLE

This paper provides a method to identify which areas on a vibrating cy lindrical shell body radiate to the far field. Of particular interest is the identification of these surface ''hot spots'' (as a function of frequency) from pressure measurements made in the far field on a circ le with the source at the center, located in the same plane as the axi s of the shell. In this paper a simple formula is derived using a rigo rous mathematical approach for the backpropagation of this far-field d ata to the surface of the shell. The accuracy of this approach is test ed with numerical and experimental data. It is shown over a wide frequ ency range that far-field data can accurately predict the acoustic sou rce regions on the shell in the same plane as the measured data. These regions are quantified using a new concept, supersonic acoustic inten sity. Implied in the success of this approach is a general rule that a coustic sources on a cylindrical body which radiate to the far field, radiate dominantly in the direction defined by the plane passing throu gh the shell axis and the source.