Dispersion and absorption of sound in monatomic gases: An extended kineticdescription

The problem concerning the propagation of plane harmonic waves of small amp litudes in monatomic ideal gases is studied using an extended kinetic model that replaces (in the same manner as in the Bhatnagal-Gross-Krook model) t he Boltzmann collision operator with a single relaxation-time term. Numeric al results for the speed and attenuation of sound are derived and compared with the experimental data of Meyer and Sessler, Greenspan, and Schotter fo r monatomic gases. At low frequencies, the correct continuum limits for the absorption and dispersion are recovered, while ai high frequencies a compl ete agreement between theory and experiments is observed. (C) 1999 Acoustic al Society of America. [S0001-4966(99)04912-7].