Turbidity in future high-frequency sonar performance models

Abstract

Current sonar performance models are incapable of accurately predicting the performance of high-frequency sonars in highly variable turbid coastal waters. There is therefore a requirement for improved models incorporating the additional effects in such environments. Turbid coastal waters are characterized by relatively high levels of suspended particulate matter, the presence of which leads to increased attenuation through viscous absorption and scattering, leading to a significant reduction in the detection range of high-frequency active sonars at moderate concentrations. The additional attenuation mechanisms have been incorporated into a propagation-loss model and the effect on detection range has been investigated. The additional attenuation processes are influenced by the ambient temperature, pressure, and salinity, and the effects of these parameters on the total attenuation in seawater containing suspended mineral particles has also been investigated. The results presented demonstrate that the effects of suspended particulate matter should be included in future high-frequency sonar performance prediction models in turbid environments. Temperature is found to be an important factor influencing the attenuation, and the local temperature should therefore be used in performance calculations. [Published with the permission of the Controller of Her Britannic Majesty’s Stationery Office.]