Abstract
The velocities of air-coupled ultrasonic propagated through the axial and horizontal directions of air-dried Japanese cedar and Japanese cypress were experimentally investigated. Composite monolithic transducers with a natural frequency of 200 kHz were used. The transducers were connected to a pulser receiver, preamplifier, and personal computer. Averaged ultrasonic wave velocities in the axial direction of Japanese cypress and Japanese cedar were about 5200m/s and 4000 m/s, respectively. The velocities for Japanese cypress were distributed ranging about 4600m/s to 5600m/s. The velocities near the pith showed the smallest values and increase toward the outside. The difference values of velocity are related to the wood structure. Locating the knot on the surface of wood specimen, it was difficult to detect a receiving waveform. Knot in wood specimen may prevent the propagation path. As above, ultrasonic wave velocities in wood could be measured with non-contact method using air-coupled ultrasonic.
