Diffraction effects in the parametric interaction of acousticwaves: application to measurements of the nonlinearity parameter B/A inliquids

摘要

This paper deals with diffraction effects related to thendetermination of nonlinearity parameters B/A in liquids using thenparametric interaction. A diffraction model, based on plane wavenexpansions, is applied to weak nonlinear interactions between twonultrasonic waves propagating in an absorbing medium. A validation of thenmodel has been carried out with an experiment performed using an opticalninterferometer. A method is proposed to measure nonlinearity parametersnwith the parametric interaction of two waves with a high frequencynratio. With respect to diffraction effects, the parametric interactionncan then be identified with a phase modulation of the high frequencynwave. A prototype, using the interaction of a 30-MHz frequencyncontinuous wave with an acoustic pulse of central frequency 2.5 MHz, hasnbeen designed. The proposed method is validated by nonlinearitynparameters measurements in well-known liquids (water and ethanol). Thenuncertainty on absolute measurements is discussed, and a relative methodnis proposed to increase the accuracy. This method enables measurementsnwithout any transducer calibration