Seismic noise in the frequency range of S-33 cycles/sechas been recorded in three mines (Haggruvan, Idkerberget, Stripa) in centralSweden at different levels down to about 750 m. As an average it is foundthat the noise amplitude decreases to 25 percent of its surface value at adepth of 50 m, to 13 percent at 100 m, to 6 percent at 200 m depth, andis less than 1 percent of the surface value at depths exceeding 500 m. Individualvariations in these numbers amount to about 100 percent in

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... ch could be explained by variations in rock properties, wave periodsand distance and direction to noise sources. The source of the noise studiedwas various surface disturbances, mainly traffic. The obtained amplitudedepthdiagrams suggest an interpretation in terms of body waves ratherthan surface waves, and the depth effect is mainly to be explained as dueto increasing distance from the noise source