Abstract: In α-LiIO₃ crystal, the attenuation coefficient of longitudinal wave is increased by an electrostatic field, if the propagation direction of wave and the acting direction of field are along the same c-axis of the crystal. The change of the attenuation coefficient with time possesses a relaxation character. We belive that this phenomenan may be caused by the interaction between the longitudinal wave and the unilaterally moving ionic carriers.