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

To examine the feasibility of using plate-type waveguides for effective det ection of acoustic emissions (AEs) from termite attacks in wood, AEs genera ted by breaking pencil leads or by termite attacks were detected using an A E sensor with a resonant frequency of 140kHz with steel plates of four diff erent sizes and thickness and three AE sensors without them. The larger pla tes were associated with larger amplitudes of the artificial AEs. The ampli tudes of AEs detected by an AE sensor with a steel plate larger than 30 x 3 0 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 detect ed by the sensor with a steel plate were much larger than those of the thre e 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 s uggest that it is feasible to use an AE sensor with a plate-type waveguide for the nondestructive detection of termite attacks in wood.