What is IEC958

Had some noise on my loudspeakers in the background from what I thought must be the electronics doing their work in the computer. Did a setup with Alsaconf but no improvement. And I cannot find out how alsamixergui and gamix should function so I went back to kmix. Playing around in functions that I could recognize I came at the advanced settings with a hole bunch of things I do not know what they should do. I decided to just kill everything that I think I do not need and to my surprise after killing IEC958 the background noise is gone. What did I kill?