Buzzing or crackling?

Buzzing could be simply large load (like a cold space heater).

Crackling would indicate an arc from a defect in wiring or insulation.

I'm never a fan of space heaters for the obvious risks that they pose. However, "buzzing" generally means something moving, and I can't see how a wire could move enough to cause enough noise for you to hear.

I'd guess that there is something (a doorbell chime, a furnace air damper, bee's nest etc.) buried in the floor that is being affected by the current draw.

I know this isn't what you want to hear, but I think you need to somehow gain access to that area where the buzzing is occurring, and figure out what it is.

"However, "buzzing" generally means something moving..."

I have heard numerous folks describe an electric arc as a 'buzzing' noise.

Smaller arc welders are often referred to as 'buzz boxes.'