The p-modes are oscillations observed at the sun surface, witch permit to probe its interior structure. These modes interact with the superficial layers of the sun. The convection zone of the sun is the source of all disturbances and thus of the oscillating wave energy .This later is transmitted through the upper layers of the sun atmosphere up to the solar corona. It is, therefore, imperative to study the p-modes propagation through these layers, knowing that in magnetized medium, these modes are confined under sun surface. In this work, we explore interaction of acoustic waves with a simple structure composed of two regions: i) non-magnetic region, ii) magnetic region. The reflected and transmitted waves and the energy balance are studied and examinated, in the aim of determining unstable modes.