Is it Okay for Switched-Mode Power Supplies to Make Noise?

[DIYLED]

I realized one thing that is different about this installation compared to anything else I've done: the components were mounted on steel inner panels inside electrical boxes. In the past I've mounted on aluminum and other materials but never steel. So the transformers or inductors and their "wingdings" (windings) could be pulling in pulses on the steel plates.

 

[ship]

Interesting, I have always used steel NEMA boxes and never seen (heard) such a thing. Not steel plates, welded box or covers bolted.