Modulus of Complex Acoustic Impedance of Air in a Cylindrical Closed Volume: Calculation Using Numerical Simulation

The influence of the effect of heat transfer between the external environment and the air inside a cylindrical closed volume with heat-conducting walls on the acoustic impedance of the air, as well as the influence on the acoustic impedance of waves reflected from the heat-conducting and thermally-insulated walls of such volumes, was studied. A numerical algorithm based on the regularized Navier-Stokes equations with a quasi-gas-dynamic closure, taking into account the viscosity, thermal conductivity, and compressibility of air, was used in order to calculate the modulus of the complex acoustic impedance of air in a closed volume with heat-conducting walls. A good correspondence was established for the values, calculated numerically and analytically, of the modulus of the complex acoustic impedance of air in a closed volume with thermal-conducting walls. The formula for the analytical calculation of the modulus of the complex acoustic impedance of air in a closed volume with thermal-conducting walls was confirmed experimentally for infrasound and low frequencies of sound vibrations. The results of the study are relevant, both for primary calibration of measurement microphones at infrasound and low frequencies by the reciprocity pressure method and the {piston}phone method, and for the study of acoustic processes in liquid and gaseous media by numerical simulation.