Originally Posted By: Dignan
Update: I asked this question on Reddit and one person suggested the possibility that my coax going into my cable box might have a different ground potential than my home’s electrical system. They suggested putting everything back to where I had the buzz, then unplugging the coax from my cable box. Sure enough, the buzz disappeared!

So now I’m going to look around my place for one of those surge protectors with coax connections in it. They said that might help.
Don’t bother with the surge protector thing.

This is the sort of thing you need.

Inline ground isolator for cable TV coax. I am sure there are numerous alternate brands at varying price points.

Typically a cable TV feed is grounded at or near the point of entry into the building. Almost by definition this grounding point will be somewhat distant from where your TV and related equipment is located. And sometimes the different grounding points develop/induce a ground loop current in the cables and directly connected equipment.

In the olden days of NTSC analogue television ground loop noise might appear as slowly rolling bands across the TV screen. And/or hum/buzz in the sound. I have corrected such problems in the pats using an inline coax isolator.

Now that you know where your hum problem is coming from, the fix should be straightforward.