The characterization of transducers for quantative NDE applications requires that the radiation pattern, conversion efficiency, and bandwidth be accurately determined. These quantities may, in principle, be determined if the transducer’s construction and constituent parts are independentiy known. However, most often the internal detai ls of the transducer are unknown and subject to statistical variations and aging. A measurement technique and system for characterizing transducers based upon external measurements is described, which does not rely upon knowledge of the transducer’s construction. Manuscript received April 19, 1976. This work was supported in p a t by the Center for Advanced NDE, operated by the Science Center, Rockwell International, for the Advanced Research Projects Agency and the Air Force Materials Laboratory under Contract F33615-74C-5180. The authors are with the Electronic Sciences Laboratory, University of Southern California, Los Angeles, CA 90007. T