A Fast Algorithm For Evaluating BEM-based Nearfield Acoustic Holography Transfer Functions

Formulation of a fast algorithm for evaluating the Nearfield Acoustic Holography (NAH) transfer functions based on boundary integral equations is presented. The new algorithm overcomes some of the well known numerical difficulties exhibited in the traditional Boundary Element Method (BEM) based NAH transfer function formulations such as excessive computational cost, non-uniqueness problem, and regularization of hypersingular integrals. The formulation is based on deriving transfer functions between acoustic field pressure and surface layer potentials using modified Helmholtz/Kirchhoff integral equations. Example problems are analyzed using both traditional and new algorithms. Solution time and NAH reconstruction results are compared to validate and demonstrate the effectiveness of the new algorithm. Finally, the acoustic holography reconstruction is applied for an automotive powerplant.