Influence of sorption on sound propagation in granular activated carbon

Granular activated carbon (GAC) has numerous applications due to its ability to adsorb and desorbgas molecules. Recently, it has been shown to exhibit unusually high low frequency sound absorption.This behavior is determined by both the multi-scale nature of the material, i.e., the existenceof three scales of heterogeneities, and physical processes specific to micro- and nanometer-sizepores, i.e., rarefaction and sorption effects. To account for these processes a model for sound propagationin GAC is developed in this work. A methodology for characterizing GAC which includesoptical granulometry, flow resistivity measurements, and the derivation of the inner-particle modelparameters from acoustical and non-acoustical measurements is also presented. The model agreeswith measurements of normal incidence surface impedance and sound absorption coefficient onthree different GAC samples