Simple, take the usual training shoe design. Add
microphones which detect all the noised made by said
footwear, the scuffs, shuffles etc. Then build in small
speakers which replay the same noise in the same
direction out of phase.... thus cancelling the original
Of course this
won't work on a long floorboard creaking on
a nail 4 feet away, but you can't have everything.
Criminals and assassins would be happy (actually, Homer
Simpson had a pair of Assassins...).
It will also serve to stop Americans calling normal trainers