In our old house we had wooden, suspended floors so I used squash balls under the turntable to stop the stylus jumping when the kids were dancing. Now we have a concrete floor I prefer the sound of superballs.
I have no idea why they work. However, this is an extract from the email correspondence that I had with Mark Gdovin, the 'inventor' of superballs for hi-fi (and microsopes):
"What I have found, Steve, is, as ruled by physics, a "conservation of energy". Until some wise-cracker disproves Einstein and Newton, we're stuck.
Yet, in the world of vibration, which is, after all, the same as sound, you can "cancel out" with opposite polarity forces. You can do these things.
What I have found, in my cursory study of molecular chemistry, is if you can
"turn" a vibration orthoganally, that is, turn it ninety degrees, it pretty
much does the trick. That is what the super balls do. That is, in many
ways, what Sorbothane does. Indeed, that is what the anti-static mats do.
Turn it inward and make it bounce against itself. By theory, half of all
incidence will be 180 degrees out of phase with all reflection and, by
nature, be dissipated or, "cancelled out". Of course, the energy has to go
somewhere. So, according to theory at least, it is converted to heat. But
not enough to worry about."
I don't know if this makes much sense but I hope you find it of interest.