抄録
Lamb waves are ultrasonic waves to propagate a board. Generally insert wedge in the excitation of Lamb waves between a sensor and boards, and it is necessary to set the angle for critical angle. We produced a water coupled Lamb wave sensor with water as wedge in the past. It was excited in high efficiency and was able to detect Lamb waves. However, a lot of spurious signal that affected a measurement were detected. I focused on a rubber have high decrement efficiency. A rubber has sound impedance near to water. I used a rubber because it damp spurious signal. I inspected the effect of a rubber in this announcement.
