New system / old system? New system, first thing is to take it out of the case and set it up on a table / the motherboard box (i.e. something nonconductive) and see if it still does it when you boot it outside the box.
The case was open, there are two sounds, the first came from the middle or maybe even off the MB and it sounded like dust particles or something. The second one was near the power pins, and sounded more like electricity crackling.
TBH I am nervous about starting it again maybe it could damage?
first thing I would do is clean the dust bunnies out of the case. After that I would reseat all my components and then make sure all my power connections were tight.