Over-Water Noise Propagation Study: Preliminary Assessment
Final rept. Oct 1996-Sep 1998
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH HUMAN EFFECTIVENESS DIRECTORATE
Pagination or Media Count:
The current propagation algorithms in the Department of Defense NOISEMAP assume soft grassy ground cover for noise propagation. The new noise propagation algorithm to be implemented into NOISEMAP Version 7.0 accounts for the effects of topography. The algorithm accounts for the reduced attenuation for noise propagation over a water surface by treating it an acoustically hard surface. This effectively increases the noise exposures that propagate across water surfaces to increase by 3dB. To investigate this modeled effect a noise monitoring study was conducted at Naval Air Station NAS Ja9ksonville and NAS North Island. The primary objective of the study was to evaluate this effect pn long4erm noise exposures and determine the validity of representing water as an acoustically hard surface in the NOISEMAP algorithms. A secondary objective was to observe the magnitude of variations associated with noise propagation over water. From these preliminary noise studies, some effect of over-water prnpagation was observed. The comparison supports the use of modeling water surfaces as acoustically hard as a good first approximation. This modeling approach should be incorporated into NOISEMAP. The noise data qualitatively displayed the trend that water surface can enhance noise exposure around an airfield by reducing the ground absorption however, the data collected were not sufficient to support any quantitative assessment about the exact magnitude of the effect.