The prediction of the "classical" components of acoustic attenuation due to shear viscosity and heat conduction is easy.  However, the prediction of the relaxational component of attenuation is quite challenging, since it is based on quantum mechanics and kinetic theory of gases.  The theory that we use is based on the Euler gas equations as the model of a continuous medium for a polyatomic gas mixture accompanied by nonlinear semi-macroscopic population equations for the number of molecules in a given energy state.  The theory demonstrates how the acoustic attenuation, alpha, depends on the composition for a three-component gas mixture of nitrogen, water, and methane.  (These three particular components of the gas mixture provide a simplistic model of a combustible gas in air.  The small quantity of methane is the flammable gas, while the water vapor in the nitrogen models humid air.)