Is the power supply for the speakers grounded? As in does it have the three pronged plug? Do you have a proper ground in your electrical wiring? Sometimes rerouting the speaker leads and USB cord may help.
I recently moved into a location that is near a large radio tower and now my speakers are picking up a radio station and they are now unusable. Is there any way to block it? If not are there any other speakers that I can buy that will not be affected by interference?