Sound attenuation in air–water media with rough bubbly interface at low frequencies considering bubble resonance dispersion

Abstract

The importance of incorporating the surface bubbles in acoustic modeling lies in the significant effects of the bubbly layer of the sea surface on the sound scattering, attenuation, and reflection. In the present paper, an acoustical system consisting of water, air, and bubbly water is considered and a particular approach incorporating a new version of the power-law concept for volumetric and scattering attenuation of bubbles is presented for the prediction of low-frequency damping of the sound in near-surface propagation. Sound attenuation in this system is traced in four steps and each step is considered as an individual case. Through applying the new power-law attenuation, the corresponding damping coefficient is derived. It has been shown by comparing the obtained results with experimental data that, at lower frequencies, the present model has better agreement with experiments than the theoretical model. Furthermore, a parametric study is conducted on different volume fractions and surface roughness, from which the equivalent damping coefficient of the free surface region is extracted using a mechanical and acoustical analogy to model the sound attenuation due to impedance difference, rough interface, bubbly water, and propagation range. It has been demonstrated that the present model can be used as an effective simple method for predicting the attenuation of sound in bubbly media with different bubble sizes.