  We develop a compact perturbative series for accoustic wave propagation in a
medium with a non Gaussian stochastic speed of sound. We use Martin - Siggia
and Rose auxiliary field techniques to render the classical wave propagation
problem into a "quantum" field theory one, and then frame this problem within
so-called Schwinger - Keldysh of closed time-path (CTP) formalism. Variation of
the so-called two-particle irreducible (2PI) effective action (EA), whose
arguments are both the mean fields and the irreducible two point correlations,
yields the Schwinger-Dyson and the Bethe-Salpeter equations. We work out the
loop expansion of the 2PI CTP EA and show that, in the paradigmatic problem of
overlapping spherical intrusions in an otherwise homogeneous medium, non
Gaussian corrections may be much larger than Gaussian ones at the same order of
loops
