I have to confess I’m a little shocked at the consideration being given to these rude and inconsiderate people.
You are entitled by law and (probably) by by-laws to “the peaceful enjoyment of your lot”.
Once somebody knows that their noise, regardless of its cause, is disturbing you, then it’s only reasonable to expect them to do something about it. That they have chosen not to means you may now feel free to be at least as inconsiderate as them.
This is what I would do.
First, I’d send them a note saying that they are in breach of the by-laws, strata laws and local council noise laws and you are giving them one final chance to pull their heads in.
I would explain that, in case they didn’t know it, by being in breach of these laws and by-laws they could be subject to fines. Also, if they are found to breached strata laws and by-laws then they are in breach of their lease and could be evicted.
But none of this is necessary if they just showed a little consideration for their neighbours. It’s their call: Pull their heads in or start thinking about where they are going to live next.
If that doesn’t do the trick, I’d drag them and their landlord through Fair Trading and NCAT, call the police very time they made a peep after 10pm and generally make them want to move out rather than wait to be evicted … all with an apologetic smile that said “I tried to warn you …”
But maybe that’s just me.