Have you tried different USB ports or a different USB cable? I'd look for a USB cable with a "ferrite choke" on it. That's the little nodule that's on either or both ends of the USB B to A cable. See if something like that helps, if not I'm not sure what the issue could be. Is the buzzing coming from a powered speaker or your headphones or what? Do you have your cellphone nearby when this happens? Sometimes those can cause a weird buzzing sound....
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