This sound is quite annoying...
To replicate (tested with no addons or libraries enabled):
Visit a target dummy with Yandir's Might (5) equipped.
Auto attack until 10 stacks of Giant's Endurance are gained. Your character's arms will radiant white bolts and an electrical grinding sound will begin.
Heavy attack to gain Giant's Might.
Continue auto attacking and heavy attack once or more times during Giant's Might 15-second duration. (I heavy attacked twice: once at 9 seconds remaining and another at 4 seconds remaining.)
Run away from target dummy to exit combat.
The sound will continue until logging out or changing zones. (And if you're in the overworld, it gets old very quickly...)
Thanks for the quick fix! I'm losing my mind here.