MEASUREMENT OF THE SOUND-VELOCITY IN LIQUIDS USING A LEAKY LAMB WAVE TRANSDUCER COMPOSED OF A LAYER-STRUCTURED SUBSTRATE

A leaky Lamb wave transducer composed of a thin piezoelectric ceramic plate and a thin glass plate is described for the purpose of measuring the sound velocities in liquids. The propagation characteristics of l eaky Lamb waves are numerically analyzed first and the operational cha racteristics of the transducer are experimentally demonstrated by meas uring the frequency dependence of the admittance and the radiation ang le of the longitudinal wave into the liquid. The sound velocities in t he saline solution of different concentrations an estimated by sweepin g the operation frequency. This transducer has an operation mode with a wide frequency range in which three propagation modes of leaky Lamb waves are involved, which is favorable for this application.