  Acoustic wave propagation in single crystals, metamaterials and composite
structures is a basic mechanism in acoustic, acousto-electronic and
acousto-optic devices. Acoustic anisotropy of crystals provides a variety of
device performances and application fields, but its role in pre-estimation of
achievable device characteristics and location of crystal orientations with
desired properties is often underestimated. A geometrical image of acoustic
anisotropy can be an important tool in design of devices based on wave
propagation in single crystals or combinations of anisotropic materials. We
propose a fast and robust method for survey and visualization of acoustic
anisotropy based on calculation of the eigenvalues of bulk acoustic wave (BAW)
diffraction tensor (curvature of the slowness surface). The stereographic
projection of these eigenvalues clearly reveals singular directions of BAW
propagation (acoustic axes) in anisotropic media and areas of fast or slow
variation of wave velocities. The method is illustrated by application to three
crystals of different symmetry used in different types of acoustic devices:
paratellurite, lithium niobate, and potassium gadolinium tungstate. The
specific features of acoustic anisotropy are discussed for each crystal in
terms of their potential application in devices. In addition, we demonstrate
that visualization of acoustic anisotropy of lithium niobate helps to find
orientations supporting propagation of high-velocity surface acoustic waves.
