I set up my recording PC (a Pentium 3 with nice quiet fans) in the quietest corner of my bedroom but for lack of furniture I had to put it on the floor. As soon as I powered on, I noticed a very deep humming coming from the direction of the machine.
I went over and lifted the machine off the carpet and found that that, without the floor reverberating, the hum was significantly reduced. Of course, you can't just suspend a PC in mid-air (at least, not on my budget) so, not really expecting it to work, I got four plastic bottle caps and placed them under each corner of the base.
How come this worked? Does the increased pressure on each leg actually supress vibrations? Or could it just be that the epicentre of the disturbance is somewhere in the centre of the base?
