Abstract: The nonlinear effects of sound in a fluid describing by the Maxwell model of the viscous stress tensor is the subject of investigation. Among other, viscoelastic biological media belong to this non-newtonian type of fluids. Generation of heating of the medium caused by nonlinear transfer of acoustic energy, is discussed in details. The governing equation of acoustic heating is derived by means of the special linear combination of conservation equations of fluid motion in differential form. The method to derive the governing equations does not need averaging over the sound period, and the final governing dynamic equation of the thermal mode is instantaneous. It is valid for both periodic and aperiodic sound. The efficiency of acoustic heating for different shapes of acoustic wave is evaluated.