Analysis of Phase-Distorted Scattered Ultrasound with a Two-Dimensional Receiving Array

This thesis addresses the physics underlying experimental measurements of energy-related acoustic parameters in phase -distorted ultrasonic fields. The effects of phase-cancellation on experimental measurements of scattered and specularly reflected ultrasonic fields are investigated as are characteristic properties of these fields. Emphasis is placed on the comparison of phase-insensitive and phase-sensitive analyses of ultrasonic fields measured with a two-dimensional receiving array. One of our underlying hypotheses is that more reliable estimates of the energy contained in an ultrasonic field, arising from the interaction of ultrasound with a material, should result in an improved characterization of the material's properties. Conventional ultrasonic receivers and receiver arrays are susceptible to phase -cancellation effects, and therefore, resulting measurements may underestimate the amount of energy contained in an ultrasonic field. A two-dimensional receiving array is employed to measure scattered and specularly reflected ultrasonic fields. Phase-insensitive and phase-sensitive methods of estimating scattered energy are applied to measurements of the ultrasonic field in the presence of intervening phase-distorting media. Specific focusing techniques, including spherical and correlation focusing, are applied to the two-dimensional receiving array and the results compared. Furthermore, we investigate how characteristic properties of the fields, such as the spatial distribution of power and the correlation of the field over the receiving array, can affect energy-related measurements.