On discontinuity waves and vibrations in thermo-piezoelectric bodies

With regard to a body composed of a linear thermo-piezoelectric medium, referred to a natural state, we consider processes for it con- stituted by small displacements, thermal deviations and small electric elds superposed to the natural state. Any discontinuity surface of order r>1 for the above processes is characteristic for the linear thermo-piezoelectric partial dierential equations. We nd the ordinary dierential equations of propagation of gen- eral standing waves and plane progressive waves. We characterize the regular waves that are reversible in time.