Ultrasonic near field in lossy media: method of simulation

Abstract

Transient ultrasonic field generated by finite aperture is strongly influenced by frequency dependent attenuation of media. The method of near field simulation in such a lossy media is presented. Significant differences between attenuation of ultrasonic waves which came to a particular field point from particular points of aperture, because of the near ultrasonic field (Fresnel zone). Urison type integral transformation was used in transient field calculations. Digital algorithm was developed and field distributions were compared in two cases: when causal model of frequency dependent attenuation in the media was concerned and when attenuation was neglected. Exampls of calculations presented had shown that transient near field is distorted by higher degree to compere with continous wave field in the media with same losses.