Analysis Of Underwater Sound Field By A Source Above The Air-Water Interface

There are important meaning to exhaustive research and grasp on the distribution rule of underwater sound field by a source above the air-water interface. This thesis is to simulate and analysis the underwater sound field by a source in the air using ray theory and normal mode theory.Firstly, investigation of the effect that air-water interface has on the transmission of sound wave into water from an airborne source. The amplitude of transmitted pressure is twice as big as the incident pressure,but the sound intensity loss increases about 30dB close to the interface. Find the intensity relationship between the source and underwater sound field.Obtained the conclusion and limiting condition of that airborne source can be replaced by a waterborne source nearby the surface; By spherical wave decomposition to obtain an expression of underwater lateral wave?an normal-mode expression of the underwater sound field by an air source and an approximate representation for depth-averaged transmission loss of underwater sound field. Study shows that lateral wave's amplitude decays according to exponent along with depthSecondly, simulated the air to water problem with a normal mode underwater acoustic propagation code and compared the result to ray theory. Including: The contribution of leaky modes on near field; The effect of effective source depth and airborne source height on underwater sound field; Comparison of transmission loss caused by waterborne source and airborne source; The effect of changing seabed types on transmission loss; Verified the depth-averaged transmission loss caused by a high frequency airborne source.Finally, finished the underwater sound field computing software development with VC++ and Fortran computer language, which can compute both transmission loss and sound field distribution.