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An analytic-numerical method to simulate the interaction of time-harmonic ultrasonic waves with imperfectly bonded layered structures is presented. In the proposed formulation, elastic layers may be either isotropic or anisotropic and adhesion interfaces are replaced by equivalent continuous distribution of normal and transversal springs. In addition, adhesion imperfections are allowed to be localized in space and are modeled by a corresponding local reduction in spring constants. The resulting direct scattering problem is formulated as a least-squares problem and solved accordingly. The formulation was extended for three different cases: Scattering from imperfectly bonded half-spaces, scattering from imperfectly bonded layered structures and scattering from imperfectly bonded layered plates immersed in acoustic fluid, and numerical simulations corresponding to each one of these cases are presented. The simulations indicate that the method is capable of capturing the scattering resulting from the interaction of ultrasonic waves with defective bonds as well as indicate that ultrasound has the potential of revealing the presence of defective bonds and interfacial heterogeneities.