Of course sound travels sideways and in apartment blocks, it can move in other mysterious ways too. Most apartments on the same floor are sitting on the same concrete slab so you can see how that would be the case. If he has put the boards directly on to concrete he has turne his flat into a giant xylophone.
The retrospective approvalists need to understand that they are opening a can of worms that might come back and seriously affect them when another renovator uses this by-law breach as a precedent to do what they want.
I would be saying to the floor board installer that he needs to pay for acoustic engineers (chosen by the committee) to conduct sound tests to establish the exising sound insulation levels in the building in non-affected flats, and then the level of sound insulation in his flat in relation to all the flats around him.
Do not accept the bog-standard BCA ratings as the benchmark for your block – it has to be the level of insulation that everyone bought into … unless you want to turn your unit block into a cheap and cheerless Lego block such as we have seen popping up (and falling down) all over our cities.
If … sorry, when the floorboard guy refuses, start proceedings at Fair Trading to have the carpet re-installed. That is the only way your committee will be taken seriously.
If the guy had done as much research on your by-laws and strata law, as he must have put into finding the cheapest flooring, he wouldn’t have this problem.
The music question is different, and I’d be issuing Notices To Comply if it is at all intruding on other residents’ peaceful enjoyment of their units.
It sounds like this person really shouldn’t be living in an apartment but that doesn’t mean everyone else has to conform to his selfish standards.