Physical mechanisms of acoustic suspension of aerosol particles in the gravity field under the effect of the traveling and standing sound waves are analyzed. The equations of particle equilibrium are obtained taking into account these mechanisms. These equations establish the relation between the properties of the sound wave, aerosol particle, and gas, so that the particle levitation averaged over the period of oscillations realizes. The parameters of equilibrium are calculated numerically for a water drop suspended in air, depending on its size. Based on numerical calculations, the contributions of various mechanisms to the particle suspension conditions are revealed for the traveling and standing sound waves at different Knudsen numbers.