What is that blackbox behind the fan on one of the pics in the "Adding Fan Speed Control::written by::Macroman::dated::10th Dec 2001"-article? I suppose it's a dust-filter, but it's HUGE!!!! Anyway, I like that and can imagine that this baby keeps the noise in as well as it keeps the dust out! Any comments on that? Or maybe someone who knows where I can find more info on that bbb (black box baby)?