为感谢惠俊英老师的谆谆教诲，特为好奇诸君奉上水声物理--海洋传播声场模拟的一份武林秘籍！
当好奇诸君阅毕此卷，再对照轻松跑完六份作业（六路招式），即入“水声物理”之江湖！
BELLHOP与AcousticsToolbox遵照GNU公共许可证进行分发。感谢Michael B. Porter对BELLHOP的原创，也感谢Orlando Camargo Rodríguez此份大道至简的入门秘籍。更感谢由Free Software凝聚起来的自由科学家社区。(Bellhop is a highly efficient ray tracing program, written in Fortran by Michael Porter as part of the Acoustic Toolbox (available at the website of the Ocean Acoustic Library). Bellhop is designed in order to perform two-dimensional acoustic ray tracing for a given sound speed profile c(z) or a given sound speed field c(r; z), in ocean waveguides with flat or variable absorbing boundaries. Output options include ray coordinates, travel time, amplitude, eigenrays, acoustic pressure or transmission loss (either coherent, incoherent or semi-coherent).)