Has anyone insulated to cut down on furnace noise?

Yes, reading about that now. They talk about affixing sound-proofing material to the walls of the enclosure but there is no enclosure. Just a board under and above it. the sides are open and go off into the basement. Could I say....velcro some soundproofing material to the areas of the furnace that are just metal housing and not vents? Would that help at all? And maybe put some across the front but not covering where the heat exits the rig through the outside wall?