The best way to soundproof a floor is to:

  1. Improve the mass of the floor to help block airborne noise
  2. Improve the ability of the floor to absorb sound energy and vibration (footsteps). Without this, the addition of mass will have very little effect on helping to block impact noise
  3. Use acoustic insulation (such as acoustic mineral wool) between timber joists to eliminate sound resonating and amplifying in this potential sealed chamber
  4. Use different materials of high mass. Different materials perform better for different sound frequencies, so using a combination of high mass materials will perform better than simply more of the same material