There is also the focal statistics way. Something like:

    Con(IsNull("your_raster_with_voids"), FocalStatistics("your_raster_with_voids", NbrRectangle(4,4,"CELL"), "MEAN"),"your_raster_with_voids")

used in the raster calculator.

You could change NbrRectangle and MEAN to find different solutions. I tried to use NbrCircle and MINIMUM instead, but I never got satisfying results.