This study presents numerical simulation and experiment to investigate the vibration characteristics of a transducer used in an immersion ultrasonic testing. Firstly, the Rayleigh-Sommerfeld integral is used to numerically evaluate pressure waves excited by a transducer in a fluid, on the assumption that the velocity distribution on the vibration plane of the transducer is given. The results show that the velocity distribution influence the so-called ring source waves generated at the edges of the transducer. Secondly, an inversion method is developed to determine the vibration characteristics of a transducer when pressure waves are given at several points in a fluid. It is shown that the velocity distribution on the vibration plane is well reproduced by applying the inversion scheme to simulated near-field data. The inversion method is then applied to experimental data.
