Try a ground lift
Not sure if this is the same problem, but, in some clubs we get this almost helicopter noise as soon as the PC boots up. A ground lift on the PC alone will usually solve it. If it doesn't, plug everything into 1 power strip & put a ground lift on it.
If you have a battery in your PC, you can unplug the PC & see whether the noise goes away, which would confirm the problem has to do with the electrical source grounding.
Wayne
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