Two-unit strata plans are the hardest to manage because it’s always one person’s opinion against the other’s. There are legal avenues you could explore through Fair Trading and the CTTT but they are long, arduous and even if you get the result you want, it will be at the expense of your relations with your nearest neighbour.
You could try the softly, softly approach and say:”let’s assume you’re not the noisiest people in the world and we’re not the most noise sensitive” and see where you get. Invite them to turn the “dumb waiter” (is that a dishwasher?) on and come into your unit and hear how loud it is. The same goes for scraping chairs.
If need be, think about going to free mediation at a Community Justice Centre (https://www.cjc.nsw.gov.au/cjc/com_justice_index.html).
If that fails and you have a by-law that forbids interfering with the “peaceful enjoyment of another lot” and they are running loud domestic equipment late at night, they are in breach. If they’ve installed timber or tiled floors while you were away, and that is causing a noise problem, they are in breach too.
So check your by-laws, then ask them what they can do so they aren’t in breach (like run their equipment at reasonable times take off their shoes, and put rubber or felt tips (available at any hardware stores) on their furniture.
At the end of the day, if it becomes unbearable, you may have to take the issue to Fair Trading and ask them to issue a Notice To Comply which carries a fine if the problem continues.