There's another fuzzy rule of thumb there. Tap it with a pencil. If it makes a recognizable noise, then soundproof it, particularly if it's close to the microphone. The Neewer mic arm/boom is spring loaded and I expect it will ring like a bell if you smacked it. So soundproofing is good.Neewer mic arm/boom is wrapped with some thick interfacing material.
My mic boom is a counterweighted type with no springs.
So it just makes dead sound when hit, but it takes a lot more room.
Koz
