Three-dimensional sound pressure field measurement using photoelastic computer tomography method

A photoelastic computer tomography method is developed to determine the three-dimensional sound pressure distribution of a longitudinal wave. An acoustic wave emitted from a probe gives a three-dimensional sound pressure distribution that depends on the ultrasonic transducer used. Since the sound pressure distribution affects the results of the ultrasonic measurements, the authors have experimentally studied the sound pressure distribution using a photoelastic ultrasonic visualization system. Hence we have developed a highly sensitive visualization system for the quantitative measurement of a weak emitted wave. However, since this method utilizes photoelasticity, the estimated sound field is limited to a two-dimensional one. In this study, the basic measurement system and the analysis algorithm for ultrasonic visualization have been improved to measure the three-dimensional propagation in solids using the computer tomography technique based on the two-dimensional photoelastic ultrasonic visualization technique. Using this system, three-dimensional sound pressure distribution of a commercial probe in the near field and/or far field are measured and compared with the results of the theoretical estimations.