Measurements of scaling properties for acoustic propagation in a single pore

Abstract

An experimental investigation of sound propagation in a single pore of circular cross section is described. By working at low frequencies and in various pressure ranges, viscous and thermal penetration depths which range from less than, to much greater than, the pore radius are achieved. The system is an experimental model for a pore in either sound absorbing material or the “stack” region of a thermoacoustic engine. The measured acoustic response compares favorably with theoretical predictions. Deviations are attributed to the cell geometry. In certain ranges of pressure and frequency, simple scaling properties may be utilized to determine the relative viscosity and thermal diffusivity of gases. Measurements of both quantities (relative to those of argon) for helium, neon, nitrogen, krypton, and water vapor (viscosity only) are presented and compared with known values. Practical applications of the experimental technique are discussed.