Numerical Simulation and Dual Experimental Mapping of Acoustic Field Generated by Ultrasonic Transducers

In recent years, a laboratory noncontact excitation method using the focused ultrasound radiation force generated by ultrasonic transducers has been exploited to excite vibrations of structures, and may be potentially used for experimental modal testing. However, the inability to monitor the real time radiation force prevents this approach from being applied as a practical technique for measuring the frequency response functions (FRFs) in modal testing. This work aims to obtain a thorough understanding of the acoustic field generated by ultrasonic transducers. A boundary element model using the Rayleigh Integral and boundary element method is built to simulate the generated acoustic field. The vibration of the sound emitting surface of an ultrasonic transducer is characterized, and velocity profiles are obtained at three different frequencies and are used to calculate the generated acoustic field. A microphone array and a fiber optic acoustic sensor are constructed to measure the FRFs of the sound pressure with respect to the drive voltage in two sets of four plane slices in the acoustic field before the transducer, and sound pressure profiles are obtained. In comparison to the simulated acoustic fields, the experimental results show a good agreement and demonstrate an exceptional mapping capability of the fiber optic sensor.