Impact noise insulation
My neighbor downstairs complained about the noise from my apartment. That was a tedious problem. The timber parquet was badly laid and creaked while walking and everything falling on the floor could be heard through the 150mm concrete slab and wake up a sleeping man. The solution was taken - the parquet was removed, noise insulation was installed on the slab, and the problem was resolved. It was two years ago and no complaints have been made ever since.
Sometimes installing a thicker carpet partially solves the problem.