As loathe as I am to comment upon strata matters in a State other than NSW where I'm allegedly a “Strata Guru”, I'll kick things off by firstly suggesting that Strata Laws in our (still) great Nation vary so much between States that you'd think each was indeed a different Nation.
That said, in NSW items such as split-system or compact (window rattler) air conditioners that were installed in a Common Property wall prior to the formation of the “Body Corp” would be classified a “Lot Owners' Fixtures”, that (again in NSW) are often covered for damage due defined events under the Plan's Insurance Policy, but are the Lot Owners' responsibility in terms of on-going maintenance / repairs.
Perhaps QLD Strata Laws are at least similar, even though that similarity may not be what you were hoping for! That said, there must be a way to quieten the operating noise of the air conditioners irrespective of who's responsibility that may be.