Modeling marine mammal sound exposure levels due to ship traffic noise.

Abstract

Noise due to ship traffic is a pervasive component of the global and local ocean noise from 10 to 500 Hz, but little is known of its effects on marine mammals because such effects depend on the sound exposure levels at a given location. The approach presented here consists of modeling the sound field due to various spatial distributions of noise sources located 5–10 m below the sea surface. We approximate a three‐dimensional sound field by computing the sound propagation from each source along a prescribed number of two‐dimensional vertical radial slices of a range‐dependent environment, which includes bathymetry, seafloor geoacoustic properties, water column sound speed profiles, and sea surface roughness. Propagation results from all sources are incoherently summed to form the overall sound exposure map. By varying the density of ships in a given area we can simulate the effects of shipping lanes and assess how the characteristics of the underlying seafloor alter the results.