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

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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.