Abstract: A phenomenon was observed during an experiment conducted in the Northwestern Pacific, which showed that the energy of the received signal around the sound channel axis was significantly stronger than that at other depths. To analyze the effect of a slope on sound propagation, we consider two scenarios: the source near the sea surface and the source near the bottom. As illustrated by numerical simulations, the sound wave decays fast in a range-independent environment when the source is located near the sea surface. However, the presence of a continental slope enables the acoustic signal to propagate to a very long range, which is also true for the case where the source is located near the bottom. Moreover, as the source is located near the bottom, the continental slope changes the distribution of the sound energy, making it converged around the channel axis. In this case, the multipath time spread corresponding to small grazing angles is very small.