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 t hese devices include location and imaging of objects for production en gineering and non destructive evaluation of materials. In previously p ublished work, investigation into the held characteristics of ultrason ic transducers has produced a mathematical theory that models the pres sure field variations for a plane piston transducer. With modification to the mathematical theory a model of the pressure field variations f or a range of transducer geometries and driving signals has been devel oped. The pressure held of a capacitance air-coupled transducer was me asured by scanning a miniature detector through the field. Thus, it wa s possible to compare the experimentally obtained pressure held with t he theoretical pressure held. This has enabled us to design air-couple d ultrasonic transducers with optimum characteristics for air-coupled non-contact imaging of materials.