Plate-type waveguides for detecting acoustic emissions generated by termite attacks

Abstract

To examine the feasibility of using plate-type waveguides for effective detection of acoustic emissions (AEs) from termite attacks in wood, AEs generated by breaking pencil leads or by termite attacks were detected using an AE sensor with a resonant frequency of 140 kHz with steel plates of four different sizes and thickness and three AE sensors without them. The larger plates were associated with larger amplitudes of the artificial AEs. The amplitudes of AEs detected by an AE sensor with a steel plate larger than 30 x 30 mm were greater than the average amplitude of the artificial AEs detected by three AE sensors. When detecting AEs generated by the feeding activity of workers, Coptotermes formosanus Shiraki, the cumulative AE events detected by the sensor with a steel plate were much larger than those of the three AE sensors without a plate. Because AE waves are attenuated much less in a steel plate than in wood, it is more effective to attach the AE sensor to wood with a steel plate rather than directly to the wood. These findings suggest that it is feasible to use an AE sensor with a plate-type waveguide for the nondestructive detection of termite attacks in wood.