Characteristics Of Underwater Acoustic Channel Under Ice/Snow-covered Layer

With the development of polar channel,the strategic position of the North Pole has become more prominent.But since most of the polar regions are covered by ice and snow,various activities under the ice in the water area need the support of underwater acoustic technology.Therefore,the complex acoustic environment caused by polar extreme climate urges us to study the underwater acoustic technology.The prediction and simulation of sound field is the basis of marine scientific research.In the polar regions,the upper interface is covered by ice or snow.So when sound reaches the ice/snow-covered interface,its propagation will be affected because of the reflection of ice or snow.Due to the complex structures and physical properties of the ice/snow-covered layer,the reflection process will also become extremely complex,so the prediction of sound field under the ice/snow-covered layer becomes more difficult than ice-free sound fields.To solve these problems,firstly in this paper,the single ice layer will be simplified as a homogeneous elastic body and models of the “air-Ice-water”?“air-Snow-Ice-water”will be established.Then theoretically this paper will analyze and calculate the acoustic reflection and scattering effect of the upper ice/snow-covered interface under different layer models,and summarize the influence of reflection coefficient caused by several variables,such as ice thickness,snow thickness and acoustic wave frequency and so on.The ice/snow-covered layer is a two dimensional random rough surface.This paper will study the causes of rise and downs of sea ice and the status of the keel,and introduce the common method of simulating sea ice draft profiles at the same time by using Monte Carlo method to establish sea ice undulation model on the basis of characteristic statistic parameter.On the basis of ray theory,an underwater acoustic channel model under the ice/snow-covered layer will be established.At the same time,in the same condition,a comparative study of the differences of underwater acoustic channel under the absolute softinterface,ice layer and the ice/snow-covered layer will be carried out.This paper will also analyze the characteristics of the channel under the ice through three aspects,ray tracing,transmission loss and channel impulse response.In the case of higher frequency and thicker layer,the ice reflection coefficient will be considered as a variable which only varies with the changes of the incident angle.Finally this paper will analyze and compare the horizontal correlation and the vertical correlation of the underwater acoustic channel under undulant ice/snow-covered layer and flat ice/snow-covered layer.