Ocean Ambient Noise Field Modelling and the Optimized Noise Term

Abstract

The objective of this thesis is to determine the frequency and wind-wave forcing dependent effective sea surface noise source level per unit area (NSL/A) extracted from the hourly minimum sound power levels of six month-long acoustic recordings. The effect of the propagation environment was accounted for using Bellhop. The simulated environment was configured using climatological sound velocity profiles to capture seasonal effects. Bottom sound speed estimates were made from seabed sediment maps. Hourly meteorological data were extracted from ERA5 providing relevant wind and wave parameters from which noise levels may be predicted. A weighted composite model consisting of neutral wind and significant wave height leveraging the two-term exponential regression function maximized model R2. Hourly minimum sound power level derived model-data comparisons using horizontal wind speed magnitude 10 m above sea level expressed a decrease in NSL/A estimates versus Kewley (1990) by 10 to 15 dB from 1 to 3 kHz.