Christopher J. Burkhalter
Naval Res. Lab., Code 7181, Stennis Space Center, MS 39529-5004
Various methods were explored and developed to simulate distant shipping ambient noise without executing very time-consuming sound propagation models for each surface ship contributing to the overall noise levels. The methods were developed with certain things in mind: the effects of various environments between source and receiver, the proximity of the surface ships to the receiver, horizontal directionality, source levels, vertical arrival structure, overall precision and accuracy, and substantial reductions in time for most runs. There was, of course, a direct trade-off between run times and the precision and accuracy of the answer, but because of the inherent randomness of ambient noise, in many cases the control case (i.e., a noise model with propagation model runs for each ship) differed only slightly from the much speedier alternatives developed here. Run times and results for the two methods were compared and analyzed. [Work supported by ONR, NRL, and the Univ. of New Orleans.]