I had a weird noise in my network. It went away when I disconnected my TV ethernet cable from my switch
I actually thought it was a bad tube. Took them out, tested . Noise persisted, I tried another set of tubes. It was driving me insane.
Then I started isolating upstream and when I pulled the CAT 8 cable out of the switch the problem went away.
Someone on this forum mentioned CAT 8's metal shield can cause noise. They were right. I just switched over to WiFi but I am going to try a CAT 6 this weekend. It sounded exactly like a noisey tube , random , come and go and vary in intensity