%A Quyen Tran Cao %J Journal of Science and Technology %T Underwater Sound Propagation in Tonkin Gulf using Parabolic Approximation %X The advanced technologies of SONAR (ranging or localization for instance) has to solve the problem of underwater propagation in an ocean waveguide. Among underwater sound transmission models such as ray, normal mode and parabolic approximation (PA), the last one has more potential. The positives of PA are not only in the modeling aspect of its model but also in the capability of its practical application since unequally divided layers and range dependence are taken into account. This paper investigates the possibility of the modeling of Tonkin gulf using PA. The model is converged and the results of transmission loss factor in range proved the effectiveness of the model. %V 49 %D 2018 %I Hanoi University of Industry %L SisLab3118