A method and apparatus for evaluating the end cap round transducer horn assemblies used in debubbling operations wherein the ECR THA can be evaluated off-line at both high and low power and on-line by making electrical measurements on the ECR THA. The electrical measurements are used to characterize the physical condition of the piezoelectric ceramics of the THA. A test box is employed to practice the method. The test box is connected between the THA and a signal analyzer. Power is supplied to the THA and the electrical signals across the THA are sampled. The sampled electrical signals are transmitted to the signal analyzer while maintaining the amplitude and phase relationship thereof. The sampled electrical signals are used to generate an impedance trace for the particular THA. That impedance trace is compared to a model impedance trace. In such manner, it can be determined whether the ECR THA is operational. Further, if the ECR THA is in working condition, the impedance trace can be used to determine how efficiently it is operating. This allows for an ultimate determination to be made of how well a particular ECR THA is functioning.