Gauge Invariance Approach to Acoustic Fields.

We extend the gauge invariance property of the Maxwell΄s equations to the acoustic field equations. We solve the inhomogeneous wave equation for the scalar and vector potentials and obtain the velocity field and the stress field in terms of these potentials. Gauge invariance has symmetry property. We obtain the gauge form for the acoustic scalar potential and the vector potential and demonstrate their invariant property. We apply gauge invariance to negative refraction. Acoustic field equations also possess left hand and right hand symmetry and this gives rise to negative refraction. Here we extend negative refraction to anisotropic materials. [ABSTRACT FROM AUTHOR]