An air-coupled ultrasonic matching layer employing half wavelength cavity resonance

The concept of a multi-phase, integrated layer for improved mechanical matching between a piezoelectric transducer and an air load is explored, both theoretically and experimentally. A combination of optical and scanning electron microscopy is used to identify the internal structure of a layer comprising silicone rubber and a semi-porous membrane filter. This data is then inserted in a linear model for prediction of through transmission response and the simulations compared with experimental measurements for extrapolation of the necessary materials elastic constants. Using these properties, it is possible to design a matching layer for a given application and results are presented that confirm the success of the approach.