本文针对声速测量实验中接收端声压变化的理论推导还不够完善，尤其是对相位比较法的原理解释不清楚的问题，从振幅与声压的关系出发，建立了基于声压方程的多次反射模型. 该模型利用平面简谐波函数、声压反射系数公式和波的叠加原理，推导出了接收端的声压振幅和相位随距离的变化公式，并利用该公式解释了驻波法和相位比较法测量的原理. 仿真结果表明接收端的声压振幅和相位并不是严格的周期函数，其测量的精度与声吸收系数和声压反射系数等因素有关. 最后进行了实验验证，实验测量结果与本文模型的计算结果吻合较好. 本文的研究为正确理解该实验的物理本质提供理论指导.

Aiming at the problem that the theoretical derivation of the change of sound pressure at the receiving end in the sound velocity measurement experiment is not perfect, especially the unclear explanation of the principle for the phase comparison method, a multiple reflection model based on sound pressure equation is established from the relationship between the amplitude and the sound pressure. In the model the plane simple harmonic wave function, the formula of sound pressure reflection coefficient and the principle of wave superposition are used to derive the formula of the change of the amplitude and phase of sound pressure at the receiver with distance, and the principle of the standing wave method and the phase comparison method are explained. The simulation results show that the amplitude and phase of sound pressure at the receiver are not strictly periodic functions, and the measurement accuracy is related to factors such as the sound absorption coefficient and the sound pressure reflection coefficient. Finally, the experimental verification is carried out, and the experimental measurement results are in good agreement with the calculation results of this model. This study provides theoretical guidance for correctly understanding the physical nature of the experiment.