Experimental Determination of Slowness Curves of Acoustic Surface Waves on Anisotropic Media

Diffraction effects are important in many acoustic surface wave (a.s. w) devices : delay lines, acoustic lenses, apodized filters, helical long delay lines... If the slowness curve (i.e dependance of the slowness with propagation direction) is known, theoritical prediction of these effects can be done. But in some important cases, such as Li Nb 03, the cristalline constants are not known with a sufficient precision to permit an accurate computation of the slowness curve. Two global experimental methods can be used to determine the slowness.