说明：  水声学实验 应用简正波理论求解下列声场：如下图所示波导模型，上层为均匀水层，其厚度为100m，声速为1500m/s；下层为硬质均匀海底，海面和海底均平整。点声源位于30m深处，辐射声波频率为25Hz，编程计算10m和90m深度上的传播损失，分析其差别。
(The normal wave theory is applied to solve the following sound fields: the waveguide model shown in the following figure shows that the upper layer is a uniform water layer with a thickness of 100m and a sound velocity of 1500m/s; the lower layer is a hard uniform seabed with smooth surface and seabed. The point source is located at the depth of 30m and the frequency of radiated sound wave is 25Hz. The propagation loss at the depth of 10m and 90m is calculated by programming, and the difference is analyzed.)