Nonlinear Sound Field by Interdigital Transducers in Water

概要

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Nonlinear ultrasound beams in water radiated by a surface acoustic wave (SAW) device are examined experimentally and theoretically. SAWs on an 128° $X$-cut $Y$-propagation LiNbO3 substrate are excited by 50 pairs of interdigital transducers (IDTs). The device with a $2 \times 10$ mm2 rectangular aperture and a center frequency of 20 MHz radiate two ultrasound beams in the direction of the Rayleigh angle determined by the propagation speed of the SAW on the device and of the longitudinal wave in water. The Rayleigh angle becomes 22° in the present experimental situation. The fundamental and second harmonic sound pressures are respectively measured along and across the beam using a miniature hydrophone whose active element 0.4 mm in diameter and whose frequency response is calibrated up to 40 MHz. The Khokhlov–Zabolotskaya–Kuznetsov (KZK) equation is utilized to theoretically predict sound pressure amplitudes. The theoretical predictions of both the fundamental and second harmonic pressures agree well with the measured sound pressures.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2008-05-25