Hi, I am so glad that I've 'found' out this easy fix I would like to share it as I was suffering with horrible static noise-like speaker noise everytime I moved the mouse or the cpu was being used. With the cpu idle and the speakers turned up I would hear a 'tac-tac-tac' noise.
I'm pretty sure it effected the Ensoniq es1371/1 card that I have for BeOS. First off, I knew it wasnt my sound card, because sound is clear on linux. Then I thought it could be a driver issue. But not that either. So, today I went into the Media prefs panel. Locate it from BeMenu, Preferences and Menu. Hit the 'Ensoniq Out' selection on the left panel. Now check off the 'mute' box on CD, Line, and Mic. Turned out that the 'mic' bar was cranked up higher than usual and was causing the noise. But now since it is disabled, along with others, sound is really clear now. I hope this helps someone else down the road!