Raw geophysical data generally contain spurious noise values which, if not removed, can seriously degrade any results obtained when the data are processed. Such spurious values may be caused by "environmental" noise generated externally to the data-gathering equipment; introduced by the data-gathering equipment; or introduced during preliminary data-handling (tape copying, etc.) processes. Data-manipulation steps, such as the conversion of raw stacking velocities to interval velocities, can also generate noise components which must be removed before the results can be utilized reliably.