  We study the coupled macroscopic and lattice wave propagation in anisotropic
crystals seen as continua with affine microstructure (or micromorphic). In the
general case we obtain qualitative informations on the frequencies and the
dispersion realtions. These results are then specialized to crystals of the
tetragonal point group for various propagation directions: exact representation
for the acoustic and optic frequencies and for the coupled vibrations modes are
obtained for propagation directions along the tetragonal c-axis.
