Ward identities and the retrieval of Green's functions in the correlations of a diffuse field

That diffuse field correlations are essentially identical to Green's functions is becoming widely accepted. Here, a new derivation is provided for that identity, a derivation that generalizes to a larger variety of wave systems and furthermore permits derivation of other, related but distinct, identities that may be useful. (C) 2007 Elsevier B.V. All rights reserved.