A demonstration of vibro-acoustic reciprocity, scale modeling, and panel contribution analysis

Panel contribution analysis is a rudimentary reconstruction technique in which the structure is first divided into patches. The volume velocity or sound intensity is measured for each patch, and the transfer function between a patch and a response point is measured or predicted. The contribution from a particular patch is the multiplication of the transfer function and the volume velocity. This technique was applied to two cases. In the first, the sound pressure level at a point 3 m away from a shaker-excited structure was compared with direct measurement. Transfer functions between sound pressure at the response point and the velocity of a patch were determined reciprocally. Equivalent transfer functions were also measured using a half-scale model and results were compared to those from a to-scale model with good agreement. In the second example, the technique was applied to a running generator set and the contribution from the engine, cooling fan, and muffler shell were assessed. The volume velocity and sound intensity were measured using a P-U probe and the sound pressure in the field was reconstructed assuming both correlated and uncorrected sources.