SanctSound Sound Propagation Models

The map shows the signal-to-noise ratio (SNR) calculated as the difference between predicted received level (RL) at the hydrophone and the wind-induced noise level (WN). The RL field is calculated as the difference between an assumed sound source level and transmission loss (TL), which is modeled using a Navy version of the range-dependent parabolic equations acoustic propagation model (1) and US Navy and NOAA environmental databases: High-Resolution ¼ degree Global Sea Surface Wind Speed and Climatology (NOAA); Bottom Sediment Type (Navy) BST database and Global Ocean Sediment Thickness Dataset (NOAA). Geoacoustic parameters are extracted from published sources (2). Range-dependent sound speed profiles along an acoustic propagation path are calculated from temperature and salinity climatological monthly means of the US Navy Generalized Digital Environmental Model (GDEM). The ocean bathymetry is based on the NAVOCEANO Digital Bathymetric Data Base, which has been merged with higher-resolution local bathymetry wherever available. The model runs along 360 radials to generate a pseudo-2D TL field within a predefined range from a single-frequency sound source fixed in space. Following the reciprocity principle, the TL field is interpreted as the transmission loss from moving sound sources within the predefined range from the fixed-position hydrophone (3). To estimate WN, the wind-induced noise spectrum level (NSL) at the sound source frequency is calculated from the 10 m wind speed monthly climatology using a Navy version of the Wenz curve. NSL is then converted to WN as a 1/3-octave band level centered at the sound source frequency. (1) Collins M.D., A split-step Padé solution for the parabolic equation method, Journal of the Acoustical Society of America 93, 1736 (1993); doi: 10.1121/1.406739. (2) Colosi, J.A., Sound Propagation through the Stochastic Ocean, Cambridge University Press, NY, 2016. (3) Margolina, T., Joseph, J.E., and B. L. Southall, "BRS Sound Exposure Modeling Tool: A system for planning, visualization and analysis" OCEANS 2018 MTS/IEEE Charleston, Charleston, SC, USA, 2018, pp. 1-4. doi: 10.1109/OCEANS.2018.8604911

[
  "https://sanctuaries.noaa.gov/science/monitoring/sound/"
]