Please see below the spec for the soundproofing and fire separation applied to the underside of the first floor across the whole of the GF unit.
Provide and install 2 x 15mm layers Gyproc Soundbloc boarding to ceilings fixed directly to joists with suitable drywall screws. Board joints to be staggered and taped. Install softwood perimeter and intermediate noggings as required to manufacturer’s specification. Include all downstand beams and detailing to achieve 60mins fire resistance. All joints/penetrations to be treated with fire rated mastic sealant: See bottom line from the excerpt below from the boarding technical spec.
Along with this there are additional layers of 12mm and 9mm boards applied over the top of the existing floorboards and the floor finish. From my rule of thumb calculations this would give a sound reduction in excess of 60dbA. Obviously there would be further sound reduction of the solid walls through to number 9.