Natural variations in underwater noise levels in the Eastern Grand Banks, Newfoundland

“The topic of underwater noise pollution due to oil & gas exploration is a genuine con- cern to scientists and researchers. Studying acoustic propagation from noise sources has become one of the standard environmental impact assessment criteria for offshore devel- opments. Lower level noise is also a concern when persistent and higher than naturally occurring background noise. The natural environment contributes sound through wind and wave motion, currents, precipitation, and sea ice. A two-month autonomous acous- tic monitoring program was conducted in 2015 on the Grand Banks, as part of a study to understand the impact of seismic surveys off the coast of Newfoundland. This study aims to use that data to improve our understanding of the ambient soundscape and relate the observations to known relationships between noise levels and wind and rainfall rates. A challenge with the present data is that the observations are made in shallow water where bottom and surface reflections act to increase expected natural sound levels. This increase in sound levels interferes with algorithms used to relate wind and rain to noise levels. An analytical model was used to adjust noise levels accounting for the shallow water envi- ronment. The corrected data were evaluated using algorithms for Weather classification developed by Nystuen which were used to identify the data points with sound levels asso- ciated with shipping, drizzle, rain and near surface bubbles. The shipping contamination was removed from the data sets and resulting sorted data was used to estimate wind speeds that were compared to independent observations obtained from model data provided by Department of Fisheries and Oceans, Canada.