Continuation of acoustic near-fields

This paper deals with the analytic continuation of a coherent pressure field specified on a finite sheet located close to and conformal to the surface of a vibrator. This analytic continuation is an extension or extrapolation of the given (measured) field into a region outside and tangential to the original finite sheet, and is based on the Green's function (the transfer function) relating acoustic quantities on the two conformal surfaces. The continuation of the measured pressure field is an inverse problem that requires the use or regularization theory, especially when noise is present in the data. An iteration algorithm is presented that is successful in continuing the pressure field into the tangential sheet. The results are accurate close to the original boundary and taper (decay) toward zero with distance away from it. The algorithm is tested on numerical and experimental data from a point-driven rectangular plate. Results show the successful extrapolation (continuation) of this data into an area nearly double that of the original pressure field. This algorithm is not limited to planar surfaces and can be applied to arbitrarily shaped surfaces.