Green'S Functions For Propagation of Sound in A Simply Moving Fluid

Two approaches involving the spatial and temporal Fourier transforms have been used to derive time- and space-dependent Green's functions pertinent to the propagation of sound waves in a fluid that is moving with a constant velocity v. The two approaches give rise to differing interpretations of the observations made by a stationary observer vis--vis those made by an observer moving with the fluid. The properties of the causal and the noncausal Green's functions are analyzed, and are shown to be equivalent.