Sonar performance in turbid and bubbly environments

Richards, Simon D. and Leighton, Timothy G. (2000) Sonar performance in turbid and bubbly environments. Journal of the Acoustical Society of America, 108 (5), 2562.

Abstract

The presence of both solid particles and gas bubbles in coastal waters may have a significant effect on sound propagation, particularly at high frequencies, and may therefore be partially responsible for the observed variability in high-frequency sonar performance in shallow waters. Suspended particles increase volume attenuation through the processes of thermo-viscous absorption and scattering. Microbubbles also attenuate sound through viscous and thermal dissipation and scattering. The presence of microbubbles in the water column may also modify the sound speed and result in a dispersive medium. The effects of dilute suspensions of solid particles on the sound speed may generally be neglected for practical sonar applications. Algorithms for estimating the acoustic absorption coefficient and the speed of sound in water containing suspensions of fine mineral particles and populations of microbubbles have been developed. These have been incorporated into a sonar performance prediction model based on the ray method. Results are presented from this model which show that, for populations of suspended mineral particles and microbubbles which are commonly encountered in shallow-water environments, the predicted sonar performance is significantly different from that predicted when the additional effects are not taken into account.

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