This article is from the rec.audio.* FAQ, by with numerous contributions by Bob Neidorff others.
Some complain that heavy foot falls will cause skipping or more
subtle sonic problems with CD players or turntables. If you
have these problems, there are a few different things which you
can try to reduce the problem. One is to add weight to the rack
which holds the equipment. Heavier things move slower. If you
can get the motion slow enough, it won't cause sonic or tracking
Another solution is to add rubber or elastomer (Sorbothane)
cushions under the CD player or turntable. This might make it
better, but might also make it worse. Experiment.
A third solution is to increase the coupling between the rack
and the floor using spikes, which concentrate the weight on
a very small area. Another way to increase the coupling between
the rack and the floor is to use a plastic adhesive like HoldIt,
sold under the UHU trade name in office supply stores.