USB noise & static,
This review is from: Trust MiLa 2.0 USB Speaker Set (Accessory)
Plugged these in and like other reviewers got a continuous whining/static noise. It's very quiet but there in the background.
I found the solution was to unplug the USB from my desktop and plug it into an old iPhone charger I had around. Not ideal because the point of these was to remove the need for a separate power supply, but it got rid of the noise.
This could explain why some people have issues and why some people don't.. it depends on the purity of the USB source.