If you cannot do anything to the ceiling below and you are prepared to take up your existing floorboards then an effective solution is shown below if you want to retain the existing floorboards.

Ideally acoustic mineral wool, or even better the 2FT45 should first be inserted between the joists.

Battens should be nailed/screwed into the sides of the joists at a depth equal to the thickness of the wood plank you are using. Once the battens are fixed the sections of wood plank should be cut and placed onto the battens and well sealed with acoustic sealant. Once this has been done you will end up with a flush surface, the height of the existing joists, that has been sealed airtight as well as having additional mass added to increase performance.

The IsoBase resilient isolation can then be rolled out onto the sealed base and the top T&G floor can then be laid directly onto it. Using IsoBase in this manner will only lift the original floor level by around 5mm plus the thickness of the chipboard. The thicker and denser the wood plank used the better.

Further improvements can be obtained by fixing 2 layers of 6kg T60 membrane to the T&G topfloor or even the wood plank (if floorboards left exposed).

If you wish to have your old floorboards as the finish flooring and want to install soundproofing underneath the best way is shown on the right. You need to keep the floor rise to a minimum by adding the wood plank inserts flush to the existing joist tops. Then you can lay an isolated subfloor using IsoBase floor insulation with a glued tongue & grooved base on top. The existing floorboards can then be secured ONLY to the T&G subfloor. It is essential that the screws do not penetrate the layer of insulation and go through into the joists or wood inserts otherwise the insulation will be compromised by the screw contact and impact noise will get back through again.

A small gap must still be kept around the perimeter so that the floorboards do not make contact with the walls otherwise, again, the insulation will be breached. It must still be taken into consideration that this method will still raise the floor by up to 50mm (2").