Development of non-destructive method for water content and internal defect of trees with an acoustic vibration technique

我们开发了一种新的振动技术和设备，可以获取活树的内部信息。该装置可以确定主干的第二和第三共振峰。声速与杨氏模数呈正相关，与密度呈负相关，表明声速反映了树干内部的水状况。测得的流速冬季高，夏季低，说明夏季的含水率高于冬季。雨前流速较高，雨后流速较低，反映了树干内部的水分状况。用无缺陷原木测得三次频率与二次频率之比，各点接近1.5，而有空洞或节点的有缺陷原木的频率比均在1.5以下或以上。证明了振动技术可以对树干内部的含水率等质量进行评价和检测。

We developed a new vibration technique and device that acquires internal information within the living tree. This device could determine the second and third resonant peak of the trunk. The sound velocity is known to be positively related with Young's modulus and negatively with density, suggesting that it reflects the internal water condition in the trunk. The measured velocity was high in winter and low in summer, suggesting that the water content in the summer is higher than in the winter. The velocity was also high before rain and low after rain, also suggesting that the velocity reflects the internal water condition in the trunk. When the ratio of the frequency of third to that of second was measured using a log without any defect, the ratio is almost 1.5 at every point, while those of defected log with cavity or node were below or over 1.5. It demonstrates that vibration technique evaluate the internal quality of the trunk such as water content and detects.