Measurements of dynamic compressibility of air-filled porous sound-absorbing materials are compared with predictions involving two parameters, the static thermal permeability k 0 Ј and the thermal characteristic dimension ⌳Ј. Emphasis on the notion of dynamic and static thermal permeability-the latter being a geometrical parameter equal to the inverse trapping constant of the solid frame-is apparently new. The static thermal permeability plays, in the description of the thermal exchanges between frame and saturating fluid, a role similar to the viscous permeability in the description of the viscous forces. Using both parameters, a simple model is constructed for the dynamic thermal permeability kЈ(), which is completely analogous to the Johnson et al. ͓J. Fluid Mech. 176, 379 ͑1987͔͒ model of dynamic viscous permeability k(). The resultant modeling of dynamic compressibility provides predictions which are closer to the experimental results than the previously used simpler model where the compressibility is the same as in identical circular cross-sectional shaped pores, or distributions of slits, related to a given ⌳Ј.

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The high-frequency behavior of the fluid velocity patterns for smooth and corrugated pore channels is studied. The classical approach of Johnson et al. ͓J. Fluid Mech. 176, 379 ͑1987͔͒ for smooth geometries is obtained in different manners, thus clarifying differences with Sheng and Zhou ͓Phys. Rev. Lett. 61, 1591 ͑1988͔͒ and Avellaneda and Torquato ͓Phys. Fluids A 3, 2529 ͑1991͔͒. For wedge-shaped pore geometries, the classical approach is modified by a nonanalytic extension proposed by Achdou and Avellaneda ͓Phys. Fluids A 4, 2561 ͑1992͔͒. The dependency of the nonanalytic extension on the apex angle of the wedge was derived. Precise numerical computations for various apex angles in two-dimensional channels confirmed this theoretical dependency, which is somewhat different from the original Achdou and Avellaneda predictions. Moreover, it was found that the contribution of the singularities does not alter the parameters of the classical theory by Johnson et al.

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