When i was building a super smelter, i tried removing the minecart sounds, but i noticed that only turning the friendly creatures dial to off worked.

Steps to recreate:

1. Make a rail system that will keep the minecart moving (check the picture below for help.)
2. Go to the music and sounds menu and turn off friendly creatures (Esc>Options>Music & Sounds>Friendly Creatures)
3. You will notice that because you turned off the Friendly Creatures tab, oddly you can not hear the minecart sounds anymore.