The Influence On Sonar Performance By Suspended Particles In Shallow Sea Alongshore

Sonar is used by detecting and orienting target with sound wave underwater, it plays an important part both on military use and ocean engineering. Signal-to-noise ratio and detection range are two significant sonar performance criterions. Because of sound wave's reflection from sea surface and seabed, tide, current, ambient noise, bubble, sound wave propagation under shallow sea gets so complex that performance of sonar is influenced. So the research on sonar performance prediction by suspended particles is very necessary.In seawater sound transmission loss includes geometry spread loss, medium sound absorption, interface reflection attenuation, and nonuniform object scattering. The physiognomy of our country shows the western is higher than the eastern, a large amount of mud and sand carried with river flow into the eastern littoral water area, thus this area contains more sediments. Besides, stormy wave and tidy are also main reasons which cause accretion of suspended particles. When the active sonar system detects, orients, identifies target under high concentration suspension, viscous absorption and volume reverberation inflect the sound propagation in seawater, which cause the sonar signal-to-noise ratio and detection range expression changed.The paper based on Urick's visco-inertial absorption theory, applies Pekeris wave-guide model, compares and analyzes sound propagation between suspension and clear seawater, thus gets the transform about sonar signal-to-noise ratio and detection range. According to collecting and analyzing the data of suspended particle along Chinese littoral sea, the paper tidies up suspended particles'concentration, density, radius, and components in Yellow River and Hangzhou Gulf, which are four aspects related to acoustics. At last, the paper researches the increment of volume reverberation by suspended particles, these can provide arguments to determine the background disturb where active sonar perform. The paper does numerical calculation about sonar detection performance caused by suspended particles.After analysis, we can conclude that:(1) Sonar signal-to-noise ratio and detection range increase as the frequency increases. The difference of signal-to-noise ratio and detection range between clear seawater and suspension is relative to visco-absorption coefficient.(2) Sonar signal-to-noise ratio and detection range increase as the concentration of suspension or density of suspended particle. Further more the effect from concentration is more obvious than density.(3) Different sonar performing frequency magnitude related to certain unique particle radius magnitude plays most significant influence on sonar performance.(4) Volume scattering-strength increases as the frequency, which is a linearity function. And it is also relative to the concentration, density, and radius. Within the study parameter area, volume scattering-strength changes from -20dB to -250dB.The paper analyzes the influence on sonar performance by suspended particles alongshore in theory, large mount of continuous data should be supported.