UPDATE:
I may have a ground loop issue! I used a cheater plug on the 3-prong powerline adapter and it eliminated all the noise, even during file transfers when the noise was the worst.
So, now what? Do I need an electrician? Is it unsafe to leave the cheater plug attached?
At least I found...
I am seeking advice, thanks.
I am using some powerline adapters to get "better" speed to my basement and kitchen. They do provide faster than wifi speed, at a cost, a ton of electrical noise, I'm not sure which, EMI or RFI. It is most noticeable when using headphones.
Here is the setup...