Mana, are you using an old or a new wodent wheel? Cause mine is the newer kind, and it has little raised lines instead of recessed. I think that was something they were doing with the old ones, and changed it on the newer model.
And you're right, the wheel itself is completely silent, it's just the sounds of Belgie's little feet hitting the plastic that makes noise. And for some reason she can't quite get into the rhythm of it, and so it tends to wobble out of stability for a little every once in a while, which makes a lot of noise. And I have mine attached to the ceiling, too, so let me know if leaving it on the floor gets more ratties willing to use it! Sevilla just won't, and I can't for the life of me figure out how to convince her it would be fun.