A New Technique for Characterizing Ultrasonic Transducers in Inhomogeneous Media
This work describes several extensions to the angular spectrum method of acoustic field analysis in order to account for wave propagation in inhomogeneous media. The method provides three dimensional prediction of both near- and farfield complex pressure distributions for differently shaped ultrasonic radiators, both planar and focussed. In addition, the method also models a layered inhomogeneous medium, concurrently accounting for several media properties. The approach is based on a systematic extension of the angular spectrum method; this involves modifying the phase factor to account for refraction, dispersion, attenuation and the effects of weak inhomogeneities. A computer simulation has been developed, and results for various transducer geometries and media properties are discussed. Specifically, the field patterns from focused and phase steered apertures are modelled, and propagation in media which have refractive and phase distorting properties is examined.
KeywordsInhomogeneous Medium Evanescent Wave Direction Cosine Ultrasonic Transducer Angular Spectrum
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