Translating jet noise measurements to near-field level maps with nearest neighbor bilinear smoothing interpolationa)

U.S. Department of Defense hearing conservation and noise limits standards require the definition of safe areas around all objects that emit noise and suggest various methods for characterizing these levels. The protection documents do not describe methods for reducing discrete measurement points into level fields to map safe and hazardous noise areas. For maintainers of high-powered jet aircraft, the suggested 85 dBA level contours that delineate the border between safe and hazardous regions occur at distances that far exceed normal operation positions. Conversion of discrete measurements to modeled levels defined over the entire ground personnel operational area in the aircraft vicinity is required to ensure sufficient protection. Present research offers a method to build a coarse map of grid points with nearest neighbor approximations, and then refines this using bi-linear smoothing. This nearest neighbor bi-linear smoothing approach provides predictions that are sufficiently accurate in cross-validation comparisons to the near-field locations and is the preferred method for the creation of hearing conservation contour level maps.