Low frequency ambient noise modeling in the North Pacific: Simulation versus experiment

Abstract

Farrokhrooz et al. [J. Acoust. Soc. Am., 2017] measured the seasonal variations of ambient noise in the 40–50 Hz band using long vertical arrays deployed during SPICEX, a 2004–2005 experiment in the northeastern Pacific. This talk compares simulations of low frequency noise from distant sources with the SPICEX data. The dominant sources of distant noise in the 40–50 Hz band are ships and wind. Noise from surface shipping and wind sources is transferred into the deep sound channel by several mechanisms [Dashen and Munk, J. Acoust. Soc. Am. 1984] and propagates long distances. The simulations use shipping density maps from exactEarth, Ltd., and measured wind speeds from European Centre for Medium-Range Weather Forecasts (ECMWF). A parabolic equation model that includes internal wave effects is used to generate Monte Carlo trials for different realizations of the shipping and wind environment. Results indicate that the seasonal variations in the SPICEX data are dominated by distant wind sources, including storms and persistent high latitude winds during the winter season. This comparison of simulation and experiment supports Bannister’s conclusions [J. Acoust. Soc. Am., 1986] regarding the role of high latitude winds in generating low frequency ambient noise. [Work sponsored by ONR.]