Radiated fields of an air-coupled ultrasonic capacitance transducer

The use and development of ultrasonic air-coupled transducers that can operate above 100 kHz have been of recent interest. Applications of these devices include location and imaging of objects for production engineering and non destructive evaluation of materials. In previously published work, investigation into the held characteristics of ultrasonic transducers has produced a mathematical theory that models the pressure field variations for a plane piston transducer. With modification to the mathematical theory a model of the pressure field variations for a range of transducer geometries and driving signals has been developed. The pressure held of a capacitance air-coupled transducer was measured by scanning a miniature detector through the field. Thus, it was possible to compare the experimentally obtained pressure held with the theoretical pressure held. This has enabled us to design air-coupled ultrasonic transducers with optimum characteristics for air-coupled non-contact imaging of materials.