im pretty sure its just noise floor being amplified! every electrical piece of hardware will get some type of noise when making a gain on the sound without anything being played.

Sounds like interference, presumably the SB Live is a PCI card so its inside the machine? And it will have no kind of shielding at all. I used to have terrible background noise when I was using onboard sound, I would get a high-pitched whining come through my headphones when my CD drive span up! Now Ive got an external firewire soundcard (Focusrite Saffire) and its total silence...