Index of content:
Volume 109, Issue 1, January 2001
- ULTRASONICS, QUANTUM ACOUSTICS, AND PHYSICAL EFFECTS OF SOUND 
109(2001); http://dx.doi.org/10.1121/1.1333422View Description Hide Description
A volume modulation technique is employed to measure the complex compressibility of a gas in reticulated vitreous carbon (RVC). The complex compressibility depends on the geometry-dependent thermal coupling between the gas and the solid walls, and is related to the thermoacoustic function or equivalently By measuring samples of different cross section and length, all external boundary effects are eliminated, so that corresponding to bulk RVC is determined. Working down to very low frequencies achieves a wide range of values for the ratio of the thermal penetration depth to the mean pore size. As a test of the concept of “capillary-based porous media,” the results are compared to analytical solutions for in circular, parallel plate and pin-array geometries. Measurements made at peak-to-peak gas displacement amplitudes exceeding the pore size in at least half of the sample showed no observable deviation from the small-amplitude results.