凹球面自聚焦声场非线性效应的研究

Research on Nonlinear Effects of Sound Fields Induced by Self-focused Concave Spherical Transducers

用球束方程(SBE)研究了声源参数和媒质特性对凹球面自聚焦声场非线性效应的影响。结果表明,谐波的最大幅值出现在声焦点附近,基波与线性声场的分布类似,而高阶谐波的聚焦性能更好。超声频率、声源表面初始声压幅值或非线性参数越大,即平面波冲击间断形成距离越短,声的非线性效应越明显。声衰减会使非线性效应减弱,而凹球面曲率半径增大会使谐波和基波最大值的位置偏离更明显。

Influence of various factors such as the parameters of ultrasound sources and the properties of medium on the nonlinear effects of sound fields induced by self-focused concave spherical transducers has been studied using spheroidal beam equation（SBE）. The results show that the maximum peak of harmonic appears near the acoustic focus. The distribution of fundamental is similar to the linear sound field, but high harmonics focus better. If the frequency of ultrasound source, the initial amplitude at source or the coefficient of nonlinearity increases, i.e. the shock formation distance for a plane wave is shorter, the nonlinear effect of sound will strengthen. Damping of sound will weaken the nonlinear effects, and the position shift of maximum peak between the fundamental and harmonics is more obvious as the curvature radius increases.