测量水中声速时，随着接收、发射换能器的间距增大，会出现接收声压的极大值先增后减的异常现象，且该异常增长的曲线特征与水位有关.本文通过多元高斯声束叠加的方法模拟了圆形换能器的发散声场，并利用虚声源模型，推导出接收声压与距离的解析关系式，相应的数值计算复现了水中声压幅值非单调变化的异常现象，并证实其主要来源是水中声场在水-空气界面和水-水槽壁处的反射，水面高度对异常模式的影响也被计算证实.

In the measurement of sound velocity in water，abnormal phenomenon appears that the magnitude of locally maximum of sound pressure on the receiving transducer increases as the receiver moves away from the emission transducer，which differs from the prediction of ideal model and conflicts with the common sense of attenuation in water.Furthermore，the relationship of the locally maximum pressure and the distance between two transducers depends on the height of water in the tank.To solve the myth above，the superposition of Gaussian beams and the method of image sources are applied.Equipped with the analytic expression of the relationship between the pressure and the distance，numerical simulation reproduces the non-monotonic decreasing as seen in the experiment，thus the speculation that the reflection on the interface of water-air and water-tank contributed to such phenomena is verified.