The best way to soundproof a floor is to:
- Improve the mass of the floor to help block airborne noise
- 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
- Use acoustic insulation (such as acoustic mineral wool) between timber joists to eliminate sound resonating and amplifying in this potential sealed chamber
- 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