Reconstruction of the Acoustical Impedance Profile of a Multilayer Medium

The recovery of the acoustical reflectivity function and impedance profile of a layered medium from bandlimited and noisy pulse-echo ultrasonic data is considered. The effects of the transducer and the noise are reduced using Wiener filtering. With further signal processing and a priori knowledge of the attenuation and the velocity profiles, the compensated coefficients of the reflectivity function and the impedance profile are recovered. The reconstruction techniques are presented analytically, and are also evaluated in an experimental setup composed of a conventional pulse echo system, a data acquisition and a data processing system. Under experimental conditions, the RMS errors in the estimation of the compensated acoustical discrete impedance profile were within 3% of the calculated values.