You may have bought a property that has insufficient or poor quality carpet underlay. If so, you inherit that problem and the responsibility to rectify it.
That said, if your neighbour is seriously impacted by noise it’s on them to keep a log of noise to demonstrate the impact: date, time and type of noise. I wouldn’t be rushing out to replace my carpet based on a complaint until I knew there was a serious issue, and a log will demonstrate that they are serious. If this ends up being a discussion with the other owners (assuming all four of you are on the Committee) about “old building noise” and whether something must be done about that, the other owners will want that log to show that the neighbour is seriously impacted before they start spending money on acoustic engineers.
There are other posts in this chat about measuring noise in an apartment and how to go about that. If this ever ended up in mediation, your neighbour would need to have acoustic reports. But let’s hope this doesn’t go that far.