Acoustical activity of crystals: a comparative study of three descriptions

Two apparently different descriptions of acoustical activity - one due to Portigal & Burstein [Phys. Rev. (1968), 170, 673-678] based on the concept of spatial dispersion of the elastic stiffness tensor and the other based on the rotation-gradient theory due to Truesdell & Toupin [Encyclopedia of Physics, (1960), Vol. III/1. Berlin: Springer], Mindlin & Tiersten [Arch. Ration. Mech. Anal. (1962), 11, 415-447] - are analysed on the common basis of the first-gradient theory. A relation between the tensors used for describing the acoustical activity in the two earlier descriptions is obtained.