The influence of plastic deformation of low-carbon steel on birefringence of the shear waves birefringence is examined. Acoustic measurements show that the birefringence changes monotonously, while the intensity of the change decreases with increasing strain. Significant reduction of the birefringence is found to indicate that the capability to plastic deformation has been largely used. In order to explain the experimental results, computer simulations of the crystallographic texture of a polycrystalline material, and its change during plastic deformation, have been carried out. It has been found that internal stresses due to the presence of mesodefects, accumulating at grain boundaries, have a significant effect on the crystallographic texture and the birefringence. Thus, this effect allows one condition monitoring of a plastically deformed low-carbon steels under plastic deformation.