Abstract:
Two significant recent advances in near-field acoustical holography are discussed. First, the formulation and results are presented for interior NAH used for the reconstruction of fuselage vibration, interior pressure, and acoustic intensity in an aircraft fuselage. The formulation includes derivation of a new Neumann Green function which closely matches the physics of the fluid/structure interaction and is extremely efficient for solving the inverse problem solved by NAH. Second, pertaining to exterior NAH, a method is presented which processes NAH data in order to localize and quantify radiating ``hot spots'' on cylindrical and plate structures, identifying and source ranking (using supersonic intensity) regions of the surface of the structure which radiate to the far field. The derivation of the method is rigorous, and ranks the hot spots according to their fractional (or percentage) contribution to the total radiated power. Corroborating results are presented for experiments on an internally excited, complex shell structure underwater.