Wind-dependent ambient noise level estimation in shallow water using wind speed data

Abstract

Sound is generated by the wind at sea when waves break due to the interaction of air and sea surface. Bubbles are generated in the water when waves break due to the impact on the sea surface, and a large amount of small bubbles form a bubble cloud within a few meters below the sea level. Underwater bubbles generated by wind propagate sound in all directions, which greatly affects noise in the low frequency band (<1 kHz). The objective of this study is to understand the dependence of the fluctuation in generated noise on the strength of the wind speed in coastal waters. An acoustic experiment was conducted using a self-recording hydrophone to measure wind-driven noise levels (NLs). The measured NLs, which filtered out the effect of ship noise, were compared with the modeled wind NLs over time in terms of bubble cloud depth and wind-induced source level depending on the observed local wind speed. Although a small discrepancy was observed at low wind speeds, the trend of the change in both results was in good agreement. This finding suggests that the modeling technique for estimating the wind NL using wind speed can reflect the wind-driven environment of the ocean.