Yesterday I went to a friend's house, and he had set up his christmas tree, complete with electric LED lights.
The lights were LEDs, connected to the AC 110v system.
When I touched one of the bulbs, I noticed a subtle humming/vibration with my fingertips. When he turned off the lights, the vibration stopped.
Other people touched the LED bulbs and didn't notice anything, they thought I was going crazy.
Question is : could the on-off-on cycle of AC current cause this vibration?