This paper deals with two problems concerning wave propagation in non-homogeneous media. The non-homogeneous media is modelled as one-dimensional phononic crystal. First problem is the determination of the low frequency passband. The second one is evaluation of the transmission ratio of the waves that propagate through the boundary of non-homogeneous periodic media. For the first problem low frequency passband boundaries are studied for the waves travelling along one-dimensional multicomponent periodic medium. And for the problem of wave transmission from the homogeneous medium into the one-dimensional multicomponent periodic medium dependencies of energy reflection on parameters of incident wave and medium properties are obtained and analysed.