抄録
To estimate the Young’s modulus or internal defects of wood with a non-destructive test using an ultrasonic velocity, the factors contributing the velocity need revealing. The detailed distributions of the ultrasonic velocity, measured with a measuring instrument and particular pointed sensors, show as follows: Of the three directions of wood grain, the ultrasonic velocities increase in the order tangential, radial, longitudinal directions. In the longitudinal direction, the velocity around the pith is slower remarkably. A slit between two sensors extends the transmission path, and thus slows the ultrasonic velocity.
