In this paper the Boundary Element Method is used to calculate the free-field correction for a Laboratory Standard condenser microphone (type LSI). The calculations are initiated by a numerical investigation of the convergence of two boundary element formulations - using linear and quadratic elements - on a cylindrical geometry, which is close to the actual geometry of the microphone. It is demonstrated that the pressure exhibits an r{sup}(2/3) behaviour near a right angled edge - r being the distance to the edge. This singularity is modelled using a generalized quarter-point technique, which is shown to speed up the convergence of the quadratic formulation considerably. The calculations are then compared to very accurate measurements, and the numerical modelling is further refined by the use of a coupled structural-acoustic model that takes the movement of the diaphragm into account.
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