It is postulated that the noise background of a typical seismogram is the result of the arrival at random times of a large number of small reflections which are reflected from small scatterers distributed throughout the Earth. It is shown on the basis of this assumption that if one knows the shape of a typical reflection, one can calculate the statistical parameters of the seismogram trace. Conversely, if one has the experimental autocorrelation function, the shape of the individual reflections can be determined. This analysis has been applied to a vertical spread of three geophones located 10, 75, and 125 feet below the surface. The shapes of the individual reflections were determined for the two deeper geophones. These curves show that the disturbances detected by the deeper geophone have a significantly smaller dominant frequency.