N2 - Weakly nonlinear sound propagation in a gas where molecular vibrational relaxation takes place is studied. New equations which govern the sound in media where the irreversible relaxation may take place are derived and discussed. Their form depends on the regime of excitation of oscillatory degrees of freedom, equilibrium (reversible) or non-equilibrium (irreversible), and on the comparative frequency of the sound in relation to the inverse time of relaxation. Additional nonlinear terms increase standard nonlinearity of the high-frequency sound in the equilibrium regime of vibrational excitation and decrease otherwise. As for the nonlinearity of the low-frequency sound, the conclusions are opposite. Appearance of a non-oscillating additional part which is a linear function of the distance from the transducer is an unusual property of nonlinear distortions of harmonic at the transducer high-frequency sound L1 - http://journals.pan.pl/Content/101537/PDF/07_paper.pdf L2 - http://journals.pan.pl/Content/101537 PY - 2013 IS - No 3 EP - 362 DO - 10.2478/aoa-2013-0042 KW - Nonlinear acoustics KW - parameter of nonlinearity KW - non-equilibrium media KW - vibrationally excited gas A1 - Perelomova, Anna A1 - Kusmirek, Magdalena PB - Polish Academy of Sciences, Institute of Fundamental Technological Research, Committee on Acoustics VL - vol. 38 DA - 2013 T1 - Features of Nonlinear Sound Propagation in Vibrationally Excited Gases SP - 357 UR - http://journals.pan.pl/dlibra/publication/edition/101537 T2 - Archives of Acoustics