Air-coupled ultrasonic assessment of wood veneer

Air-coupled ultrasound (ACU) provides a valuable tool to evaluate wood samples of small or moderate thickness (<30 mm) thereby avoiding direct contact or liquid coupling. Results of through-transmission ACU measurements on wood veneer samples and related products are reported with respect to a wide variety of quality aspects. Fluctuations in the averaged received signal levels appear to be correlated to the presence of thickness and density variations, flaws and grain damage, insufficient bonding on a substrate, etc. In addition the variability of the signal levels enables to distinguish between quarter and crown areas.