非均匀介质驻波声场纹影法成像及其声速测量的改善  

Improvement on Schlieren Imaging of the Acoustic Standing Wave and Measurement of Sound Velocity in Inhomogeneous Medium

作　　者：陈水桥[1] 程诗卓 郭鹍 陆子毅 许熠辉 CHEN Shuiqiao;CHENG Shizhuo;GUO Kun;LU Ziyi;XU Yihui(Department of Physics,Zhejiang University,Hangzhou 310027,China;College of Chu Kochen,Zhejiang University,Hangzhou 310027,China)

机构地区：[1]浙江大学物理学系,杭州310027 [2]浙江大学竺可桢学院,杭州310027

出　　处：《实验室研究与探索》2020年第12期46-50,共5页Research and Exploration In Laboratory

基　　金：浙江大学高等教育“十三五”教学改革研究项目(zdjg19031)。

摘　　要：利用超声波驻波声场的声能量密度在空间呈周期分布的性质,结合纹影法,对空气介质中28 k Hz超声波形成的驻波声场进行成像,使得超声波驻波声场的某些特性可视化,进而更加精准测量其波长和声速值。用光线折射几何理论证明了光的不均匀性所导致的光的折射和弯曲程度与x、y平面内各自折射率梯度成正比,并推导了光线的偏折角计算公式。为使图像更加形象可视,在MATLAB中先对纹影图像做灰度直方图均衡化,再进行灰度-颜色映射处理,得到了较好伪彩色纹影图,使实验数据测量更加便利。最后利用本文方法推导了声速测量公式,准确测量了速度值,并用数理方法分析了仪器系统的灵敏度。The paper images the 28 kHz ultrasonic standing wave in air with Schlieren method and feature of the periodic distribution of acoustic energy density of the ultrasonic standing wave.Itvisualizessome features of the ultrasonic standing wave,in order to gauge the wave length and other factors more precisely.Besides,the paper proves that the amount of light bending is in proportion to the refractive index gradient in x,y planes separately,and derives the deflective angle formula.In order to improve the image’s quality,we first do the histogram equalization of Schlieren images in MATLAB,then the grayscale-color mapping is used toget pseudo-color images of high quality,which makes it less difficult for us to acquire our data.At last,we derive the measure equation of sound velocity,precisely measure the velocity,and analyze the sensitivity of the instrumentation system.

关 键 词：光线偏折角 声能量密度 直方图均衡化 驻波声场 纹影成像 声速测量 

分 类 号：O423[理学—声学]