Characterization of air-coupled ultrasound transducers in the frequency range 40 kHz-2 MHz using light diffraction tomography

The aim of this work was to show the applicability of light diffraction tom ography on airborne ultrasound in the frequency range 40 kHz-2 MHz. Seven d ifferent air-coupled transducers were measured to show the method's perform ance regarding linearity, absolute pressure measurements, phase measurement s, frequency response, S/N ratio and spatial resolution. A calibrated micro phone and the pulse-echo method were used to evaluate the results. The abso lute measurements agreed within the calibrated microphone's uncertainty ran ge. Pulse waveforms and corresponding FFT diagrams show the method's higher bandwidth compared with the microphone. Further, the method offers non-per turbing measurements with high spatial resolution, which was especially adv antageous for measurements close to the transducer surfaces. The S/N ratio was higher than or in the same range as that of the two comparison methods. (C) 2000 Elsevier Science B.V. All rights reserved.