Plastering over skimmed plasterboard

[Rover7895]

Our dining room party wall had it's plaster blown a few months ago and we have just had it 'sorted'.

I removed the old plaster myself and it was around 2 inch thick.

The plasterer came round and fitted two sheets of plasterboard and put a light skim over them.

Where we could hear our neighbours before, we can definitely hear them a lot more now.

Question is, what can we do now? Could we add more plaster to this wall over the plasterboard and skim or do we remove and start again?