This is one of those really fraught topics. I have run into this twice from the other side.
Once, I tried to help the unit owner. I went to her unit to listen to the noise she complained of. There was an audible noise from pipes which may or may not have had anything to do with adjacent units but it was so slight that I would not have noticed if it had not been very quiet and it was pointed out. I was young at the time, had excellent hearing and was much younger than the unit owner.
Another time more recently the complainant was bothered by his neighbour’s air-conditioner. I borrowed a sound db meter from labs where I worked. The levels, even close up, were barely above ambient noise levels in a quiet suburb. The EC said it would only do anything about it if the sound level at the boundary of his unit exceeded local government standards. The unit owner got some expert in to measure. The unit owner reported back that noise levels were far below the levels that would trigger grounds for a complaint according local government, yet he still thought we should impose a higher standard. We did not act on it and he instead installed double-glazing, which is always a good idea in any case for insulation in chilly ACT.
All this is not to say that SuzieQ might not have very reasonable grounds for complaint, unlike these neighbours of mine! I think ultimately though, the onus is on SQ to demonstrate that there is an unreasonable level of noise above some objective standard. If it is bad enough, it might be simply obvious to any visitor. Otherwise getting an objective measure or making one’s own modifications on the inside of the unit might be a way forward, I think. Whether there are modifications that would help, again requires some professional advice. The SC’s offer to share the cost of some professional advice seems quite reasonable to me, unless there is such an obviously gross problem that any visitor would agree.