[linux-audio-user] noise from soundcard

This is a little off-topic, but I hope you don't mind. I get quite a lot of noise from my soundcard. There is a pulsing that sounds something like a very fast morse code at a consistent pitch, and it's unacceptably loud. I notice variations in this noise based on how I move my mouse. At first I thought this was just because of my shoddy 5-year-old Soundblaster Live, but I have a new Audiophile 2496 and it does the same thing. Today I tried removing the stereo mini plug from my soundcard and touching it to the metal on my case. The sound was nearly identical. problem is voltage fluctuations in the metal of the case. Does this mean my case needs to be grounded somehow? What can I do to fix this problem? Josh