A non-contact method for measuring surface acoustic impedance

本研究提出了一种利用声学特性进行混凝土结构状况调查和探雷的新方法。用非接触表面声阻抗测量了试件的表面状况。主要研究了以下三个问题：(1)表面条件和声阻抗之间的关系；(2)声阻抗和表面条件与两点声压的关系；(3)一种在不干扰被测场的情况下测量声场分布的新方法。实验结果证实了通过声阻抗测量找到埋入物体的可能性。推导了表面条件与声阻抗之间的关系方程。本研究新发明了一种测量管道内声场分布的光学方法。低相干光光源和可调光路长度的组合使我们能够在纵向上以空间分辨率测量声场。总而言之，为本研究的目的奠定了理论基础和研究工具。

A new method to investigate the conditions of concrete structure and to search land mines using sound property has been proposed in this study. The surface conditions of the specimen is measured in term of the surface acoustic impedance without contact. The following three subjects were mainly investigated:(1) The relationships between the surface condition and the acoustic impedance(2) The formulation of the acoustic impedance and the surface condition with the sound pressure at two points(3) A novel method to measure the sound field distribution without disturbing the field to be measured.We demonstrated the experiments of the surface acoustic impedance measurements for a bottle embedded in a shallow land. The possibility of finding the embedded object through the sound impedance measurements was confirmed as the result of the experiment. The equations denoting the relationship between the surface condition and the acoustic impedance were deduced. An optical method to measure the sound field distribution in a pipe is newly invented in this study. A combination of a low-coherent light source and an adjustable optical path length enabled us the measurements of sound field with spatial resolution in the longitudinal direction. In conclusion, the basic theory and the instrumentation have been founded for the purpose in this study.