The analytical solutions of reflection/refraction problems for bulk acoustic plane waves at the interface between elastic media and piezoelectric media are obtained by matricant method. The analysis is carried out for interface between orthorhombic media of class 2mm (Ba2NaNb 5O15) and tetragonal media of class 4mm (BaTiO 3). With this aim, a set of joint equations of elastic medium motion and Maxwell's equations for electromagnetic waves is used. The reflection/refraction coefficients at the interface between piezoelectric media are calculated beyond the quasi-static approximation. The results obtained are in agreement with the general Snell's law for any incident bulk elastic wave angles.