声速测量是大学物理实验的基本内容之一，主要应用共振干涉法和相位比较法测量声波的波长进而求得声速，在 实际操作过程中出现了一些反常现象值得深入探讨. 本文主要观察了二次相位合成现象( 即次级波峰现象)，并结合 Mathematica 软件的仿真模拟给出了理论解释.随后简要讨论了两种方法测量的不同步现象并给出了定性的解释.

Sound velocity measurement is one of the basic contents of college physics experiments，and some special phenomena appearing in the process of practical operation are worth to discuss deeply. This paper studies mainly the two phase synthesis phenomena (i.e.，secondary wave phenomena) and proves its existence through concrete experimental measurement and gives a theoretical explanation according to the simulation numerical solution of Mathematica software. Based on the results，the principle of the resonant interference and phase comparison methods for measuring sound velocity is discussed. The asynchrony between the measurements is shown，and the qualitative explanation is given.