Acoustic absorption measurements for characterization of gas mixing

This paper demonstrates the use of acoustic absorption measurements to characterize the level of molecular mixing between gaseous mixtures. This objective is motivated by the observation that many existing methods only quantify macro-scale entrainment. Over a large range of frequencies, acoustic damping is dominated by vibrational relaxation processes. Our approach takes advantage of the fact that the relaxation frequency for a particular gas is often a strong function of the other species it is in molecular contact with. Thus, the relaxation frequency of a dual component gas mixture varies with the level of molecular mixedness of the constituent species. We present the results of example calculations and experiments demonstrating the significant dependence of acoustic absorption levels upon mixing.