Role of Gas Bubbles in the Attenuation of Acoustic Waves at the Air-Sea Interface

Gas bubbles produced by breaking waves play an important role in acoustic sound transmission. For a wide range of frequencies, the scattering is resonant in nature, and resonant bubbles scatter as well as absorb acoustic energy changing the compressibility of seawater. The present study deals with gas bubbles at the air-sea interface and their role in the attenuation and scattering of underwater sound propagation. This study leads to development of a damping model for gas bubbles as function of their size and acoustic frequency, including their role at resonance frequency covering aspects on damping mechanism due to thermal, viscous and radiation effects. The damping model estimates the variation of attenuation rate at resonance frequency for high wind speeds utilizing input from bubble population model considering geometrical aspects, and parameterizes bubble distribution at different stages of evolution. The study also estimates attenuation of sound speed in the presence of bubbles using climatology fields from the World Ocean Atlas. Finally, to assess the behaviour of random bubbles on sound attenuation, the statistical distribution function signifies that damping characteristics follows a normal distribution.