The Smooth operation smooths a horizon through the averaging of multiple inline and crossline values. This operation however does not smooth across holes, that is, a point will only be affected by its directly adjacent neighbours.

You can also add 2D/3D gather volumes to the Spectra Viewer panel in Spectra Analysis using the same ways described in Adding Data Sets for Spectra Analysis. Once you’ve added the gather volumes, you can define the settings in the Details Panel below the Spectra Viewer panel.