Effects of diffraction on the membrane response of the submersible electrostatic acoustic transducer

The authors have developed a technique for absolutely calibrating the displacement amplitudes of megahertz waves in liquids by using a liquid-immersible electrostatic acoustic transducer. They examine the effects of diffraction on the liquid-membrane coupling and absolute transducer calibration by comparing near-field (Fresnel diffraction) and far-field (Fraunhofer diffraction) measurements. Results are obtained from the measurements of absolute wave displacements in the angstrom and subangstrom range in water. The diffraction-corrected absolute sensitivity of a low-frequency (500 kHz) damped ultrasonic transducer is also presented.<>