Mechanical behaviour of anisotropic media may be seen the best through its behaviour during bulk wave propagation. Such waves may be decomposed into finite plane waves propagating along arbitrary direction n in solid. Properties of these waves are determined by dependence between propagation direction and constitutive properties of media. Three types of such waves may be distinguished in connection to three displacement vectors, which determine acoustic polarization. The most of dynamical systems are naturally nonlinear; here we are going to write Reimann-Christoffel equation. This equation represents propagation condition of bulk waves as set of three homogeneous linear equations. Materials used in present analysis are fibre reinforced with one or two families of continuous fibres. Often used represent of such materials is epoxy resin carbon fibres composite whose material constants are determined with ultrasound methods.