This paper presents a new technique to characterize the damage of a bonded component. The theoretical analysis models a damaged bond as a random distribution of small interphase cracks and cavities. Interaction of ultrasonic waves with these interfacial cracks are studied by a differential self-consistent scheme (DSS) in conjunction with the backscattering signal strength formula [1]. Here the multiple scattering problem from a distribution of interphase cracks is reduced to finding the crack opening displacement of a single interphase crack. Transmission coefficients are obtained explicitly in terms of the characteristic length, density of the interfacial defects and incident wave frequency, from the solution of a first order, ordinary differential equation. Experimental verification of the theoretical solution is performed on aluminum blocks joined by an epoxy layer with varying densities of interfacial cracks. Transmission coefficients from the epoxy layer are measured with a heterodyne interferometer. The measured transmission signals are compared to predicted values and information such as defect distribution and size is extracted.