A series of controlled high explosive shots were conducted by the Atomic Energy Commission in a salt mine near Winnfield, Louisiana, to investigate seismic decoupling theories. Two recording stations were used by the University of Michigan at various distances between 1.1 and 14.7 kilometers for a majority of these shots. Frequency analyses of the magnetic tape recordings were made and the results are presented showing the relationship of the frequency spectra as a function of charge size, distance from the source, and coupled vs decoupled shots. The smaller decoupled shots detonated in the large spherical cavities were observed to have somewhat higher predominate frequencies than the equivalent size coupled shots. A change in cavity size produced no significant difference in the shape of the spectra of the large decoupled shots.