A non-contact method for measuring surface acoustic impedance

本文提出了一种利用声特性探测混凝土结构状况和探测地雷的新方法。试样的表面状态是用非接触的声阻抗测量的。本文主要研究了以下三个方面的问题：（1）表面状态与声阻抗的关系;（2）声阻抗与表面状态与两点声压的关系;（3）一种不干扰被测声场的声场分布测量方法。实验结果证实了通过声阻抗测量发现埋置物的可能性。推导了表面状态与声阻抗之间的关系式。本文提出了一种测量管内声场分布的光学方法。低相干光源和可调光程长度的组合使我们能够在纵向上测量具有空间分辨率的声场。综上所述，本研究的基础理论和仪器设备已经建立。

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.