It's a white noise/static usually near the beginning and end of songs and fades out because the sound of the music overshadows it. I haven't changed my source at all though (the only thing it's connected to is my desktop computer, with integrated audio). Is it possible it's picking up some background noise from inside the computer?
Now the problem is that I can't be sure if this noise has only recently started or if it has been there all along. Is there anyone else with hd558s that can help?