We got a brand new fence.  Looks  fantastic.  Only problem is when the wind is strong the gate vibrates and really hums.  It's outside our bedroom wall and close to our neighbours house.  Strong winds are a regular occurrence in Nelson.

The fencing company had no ideas at all.

I would really appreciate some suggestions on dampening the vibration in a way that still allows the gate to open.

The construction of the gate is powder coated vertical steel tubes in a box section frame.  It's bolted onto concrete (not attached to the house)

I've isolated the vibration to a couple of the vertical tubes. I tried clamping rubber clamps onto a tube, but that didn't work.  Leaning a big lump of wood against the gate does, but makes it a pain to open/close the gate.

I thought about filling the tubes with expanding foam, but that requires holes so risks rust.