The electromechanical characterization of the ultrasound device in air and in the loading medium has been done by measuring the input electrical admittance, tip displacement, and acoustic pressure at different excitation levels below and above the cavitation threshold. The results of impedance measurements are fitted with a simplified theoretical model of RLC equivalent circuit describing the transducer electrical behaviour in unloaded and loaded conditions and at different driving conditions. Acoustic pressure distribution has been measured in a small sonoreactor in several measurement points, and acoustic intensity and radiated acoustic power have been estimated from RMS acoustic pressure assuming diffuse sound field. The radiated acoustic power estimated from averaged acoustic pressure signal has been compared with the output acoustic power measured using the calorimetric method at different excitation levels, and with the results of electromechanical characterization. The electroacoustic efficiency factor at extreme nonlinear driving conditions has been compared with the results of low-level impedance/transfer function spectroscopy for unloaded and loaded transducer in different sonoreactor configurations.