Aperture extension for near-field acoustical holography of jet noise

It is generally true that larger measurement apertures (relative to the source size) produce more accurate reconstructions of sound fields in near-field acoustical holography (NAH) applications. When such apertures are infeasible, numerical extrapolation of the sound field can be implemented to recover data, allowing a successful NAH reconstruction. When the limited aperture is due to a large standoff distance from the source, accurate recovery of data outside the measurement region becomes increasingly critical. In the present paper three data extrapolation methods are implemented on a simulated sound field from two extended, coherent sources. The methods are compared based on their relative accuracy of extrapolated data with distance from the measurement aperture.