The present work investigates wave propagation through a damaged interface between two elastic media. Dynamic behaviour of the deterioration or damage of an interface is described using a random distribution of strip-like micro-cracks of different sizes, a periodic array of strip-like cracks or via a distributed spring model. The wave-field scattered by cracks is calculated using a boundary integral equation method. The spring model assumes introduction of the spring boundary conditions, where stresses are proportional to the displacement jump with the proportionality given by the spring stiffness. Components of the spring stiffness matrix are defined in terms of the concentration of the defects, their typical size and the elastic properties of the contacting materials. Numerical analysis of reflection and transmission for the considered models of the damaged interface is provided.