Power Cogs' sound has 2 of issues regarding the fog of war.

1. If you do not have vision over Clockwerk as he casts Power Cogs, the sound repeats whenever you gain vision over the center of the cogs, but also fade out when losing vision.
2. If you have vision over Clockwerk while he cast it, losing vision over the cogs does not make the sound fade out. It will stay fully audible, regardless of vision. On top of this, the sound repeats like in the 1st point whenever regaining vision over the area.

It should behave like other lasting ground area spells (e.g. Acid Spray and Static Storm): The sound should fade in/out upon gaining/losing vision over the affected area. And it definitely should not repeat whenever gainnig vision over the area.