Influence Of Platform's Depth On The Passive Sonar's Performance

In order to optimize the operating distance of passive sonar in four typical hydrological conditions, this paper focuses on the influence of platform's depth on sonar's operating distance. The results of the study provide a reference for the selection of the sonar's optimal receiving depth.This dissertation's research mainly includes of three parts: 1)modeling ocean acoustic channel; 2 )ptimizing receiving depth in the mode of rays and normal-mode under the condition of even negative gradient hydrology; 3)optimizing passive sonar's receiving depth for different hydrological conditions.Firstly,a mathematic model of multi-path channel is established. using span calculation to search all the important eigenrays in the known sound field by the theory of sound ray. to determine the ocean acoustic channel impulse response unit and calculate the propagation loss of the sound field. Modal function of normal-mode is used to calculate the propagation loss in the mode of normal-mode.Secondly, a simple analysis of hydrological characteristics in the mode of rays and the spatial distribution of propagation loss is solved by the example of even the negative gradient typical hydrological conditions. In order to reduce the impact of the volatility of the sound field in the latter part of the study. the smooth solution is obtained with a minimum squares fitting. The optimal working depth is solved by quality factor for sonar threshold and the maximum range of optimization criteria. In the same research methods and procedures. optimal working depth is solved under the same hydrological conditions in normal-wave mode.Finally, considering the effect of different hydrological conditions on the ocean acoustic channel, the effects of the hydrological characteristics on the propagation loss distribution is studied. The approach to solve the optimal depth in the even negative gradient typical hydrological condition is used to calculate the optimal reception depth distribution trends in different condition. The difference between normal mode and ray theory optimal reception depth distribution trends is analyzed.