I have a M-Audio M-Track MKII (USB) and I bought a pair of Behringer studio monitors recently and using 1/4 TRS cables between them. I hear permanent noise of the cpu on the monitors, even it changes with the movements of mouse. I was using studio headphones till now and never encountered this.
Btw I use 6 socket power outlet which an UPS is connected to it and my pc is connected to the UPS. The monitors are also plugged to one of the sockets on this outlet.
One thing that I found out btw is that when I plug Behringer directly with its USB to pc there is no more noise. It seems the problem is my MAudio Interface. But what will I do with that? Should I change my usb cable?
The USB cable is unlikely to be the culprit though it's the cheapest solution so maybe worth a try. If the MAudio device supports an external power adapter (rather than just USB power) then you might try that. And try plugging it into a separate power supply than the one your PC plugs into.
The full solution is probably to invest in a higher end audio interface. For example my RME Fireface set me back £700 but I've had it for years and it does a beautiful job. Or just try different interfaces but get them through a company that has an easy return policy in case they have the same problem...