@Edhawk
(UPDATE)
Still the issue exists for me. I had proper home made SSDT's using SSDTime on Linux... USB's all mapped using Hackintool with no more than 14 ports. Nothing got rid of the issue. Last thing I thought that maybe I was under powering my PC so I might try upgrading from 650 to 850 to give me some more head room anyway regardless of the issue. My power supply started making clicking noises during intense work like video editing and it was only a few months old.
When I get back home after xmas, I will see if this resolves it.
@antieatingactivist I will give this a go! I do use a power conditioner that my computer and monitors all use. Could you explain what your process here and perhaps further describe your sound? Mine doesn't begin when the computer turns on it begins when OpenCore boot loader starts and doesn't happen on any laptops.
@Edhawk - You're probably pretty fed up hearing about Mac issues, I applaud you on your patience with people needing support. Still mythed, I guess I will re-do my SSDT's because perhaps they messed up.
What you are probably hearing is electrical interference. The noise becomes more prevalent when the graphics card starts drawing power, (maybe the CPU too). The reason it doesn't do it on your laptops is because they aren't grounded to the wall like you're desktop PSU is. I'll try to explain ground loops the best I can. When you have multiple paths to ground that are of a different length or resistance, it can cause a 60 cycle hum from the AC voltages from the wall. In our case, the hum is caused by interference from some of the computer components.
Your Computer is grounded to the wall.
Your powered monitors are grounded to the wall.
My interface is DC powered, but I have a ADAT expansion unit that is grounded to the wall. (Apogee Quartet (USB), with a Behringer ADAT expansion interface and various synths plugged into it)
And you have audio cable/USB/Thunderbolt that carries a ground connecting everything.
This is a recipe for noise and is the main reason why SPDIF optical is a good thing. No electrical connections.
I tried a power conditioner, I use balanced audio signal cables, no luck. There are Ground loop isolators that use an isolation transformer to break the physical ground from the audio signal, but these can cause some frequency roll off and high end ones can be very pricy. The more Hacky way is to make sure there is only 1 path to ground. This should be your computer.
Easiest way to experiment is to break the 3rd prong ground from a power strip and plug everything audio related into it except your computer. If it works, you might do more research and explore other less sketchy methods of ground loop elimination.
The sound I was experiencing was a quiet buzz that was amplified through the speakers. it would get louder if I scrolled a window, and if I played a 3D game, it would be very wild sounding. You would also hear an occasional chirp. This would also happen on Windows. I don't know if you have the ability to boot windows, or linux right now, but that would help eliminate any doubt about your macOS/opencore config.
