Effects of sea surface waves and wind-generated bubbles on underwater sound source localization in the Persian Gulf

Abstract

Sea surface waves along with wind lead to the formation of a near-surface bubbly layer in the oceans and cause an upward refraction of sound speed profile in the layer adjacent to the surface. This refraction enhances the surface scattering and affects the accuracy of sound field simulation, and underwater sound source localization. This research investigates the impact of sound speed profile mismatch due to wind-generated bubbles on the matched field sound source localization in a shallow-water environment of the Persian Gulf. A bubble layer and a sound propagation Parabolic Equation models are combined with a high-resolution maximum-likelihood matched field processor to calculate and analyze the acoustic pressure field and source localization in the bubbly environment. To calculate the localization error, the bubble environment is compared to the bubble-free environment in five wind speeds from 6.6 to 10.2 m/s, source depths of 10, 45, and 75 m, and nine acoustic frequencies ranging from 2 to 10 kHz. The results demonstrate that the range and depth localization errors increase by increasing the degree of the mismatch and the source frequency. However, the errors are significant only at frequencies equal to or higher than 8 kHz and wind speeds greater than 8 m/s. Moreover, the values of these errors depend on the source depth. This result indicates that the errors of the source located at a depth of 10 m are more than those in the source in depths of 45 and 75 m. The matched field processor overestimates the source range and depth. The range estimation error is less than that of depth.