Motivated by a phenomenon in an experiment conducted in the Northwestern Pacific indicating that the energy of the received signal around the sound channel axis is much greater than that at shallower depths,we study sound propagation from the transitional area(shelfbreak)to deep water.Numerical simulations with different source depths are first performed,from which we reach the following conclusions.When the source is located near the sea surface,sound will be strongly attenuated by bottom losses in a range-independent oceanic environment,whereas it can propagate to a very long range because of the continental slope.When the source is mounted on the bottom in shallow water,acoustic energy will be trapped near the sound channel axis,and it converges more evidently than the case where the source is located near the sea surface.Then,numerical simulations with different source ranges are performed.By comparing the relative energy level in the vertical direction between the numerical simulations and the experimental data,the range of the air-gun source can be approximated. Motivated by a phenomenon in an experiment conducted in the Northwestern Pacific indicating that the energy of the received signal around the sound channel axis is much greater than that at shallower depths, we study sound propagation from the transitional area (shelfbreak) to deep water. Numerical simulations with different source depths are first performed, from which we reach the following conclusions.When the source is located near the sea surface, sound will be strongly attenuated by bottom losses in a range-independent oceanic environment, yet it can propagate to a very long range because of the continental slope .When the source is mounted on the bottom in shallow water, acoustic energy will be trapped near the sound channel axis, and it converges more evidently than the case where the source is located near the sea surface. , numerical simulations with different source ranges are performed. By comparing the relative energy level in the vertical direction between the numerical simula tions and the experimental data, the range of the air-gun source can be approximated.