The effects of variability of the ground on land mine detection and false alarm rates are analyzed within the framework of a viscoelastic-layered model of the ground. A matrix technique was used to describe sound interaction with layered viscoelastic ground. The resonance method in combination with a global search method is used to estimate a set of parameters for a three-layered viscoelastic ground model. Results of the estimation show good agreement between computed and experimental data. The effect of a finite size of sound source on the acoustic-to-seismic transfer function is discussed. The effect of variability of ground properties on the acoustic-to-seismic transfer function (admittance function) is analyzed. Analysis is performed on the plane of parameters of the layered ground in a wide frequency range for all angles of incidence. It is revealed that small variations in the shear speed in the top layer of ground will not cause variation in the acoustic-to-seismic transfer function at low frequencies but may cause strong variation at high frequencies. Results of outdoor measurements of the acoustic-to-seismic transfer function are presented, and a correlation between the high magnitude of the acoustic-to-seismic transfer function in certain frequency ranges and moisture content on the surface is revealed. A simple model explaining the correlation between moisture content in the upper layer, the acoustic-to-seismic transfer function, and ground properties is suggested.