There is a fine line here and it all comes down to (as so many strata issues do) what it says in your by-laws.
If there is a by-law saying that residents mustn’t disturb other owners, then the strata committee or strata manager should have issued a notice to comply becasue while the noise doesn’t affect other owners, by-laws are being breached. If your action at NCAT goes nowhere, you could try seeking orders under section 232 to compel the strata committee to do their job in enforcing by-laws.
Otherwise you have basic strata law regarding not interfering with the peaceful enjoyment of another resident’s lot. It sound as if that’s where you are headed now. That’s the loophole that your strata committee is exploiting to absolve themselves of responsibility.
Just because the sound is capable of being transmitted doesn’t prove that it is or has been. As well as the acoustic report, you should have recordings and stat decs from visitors and other owners who will testify that they have heard intrusive noise.
My car is capable of going 200kph – but I don’t get a speeding ticket just for owning it. There is a behavioural element in noise nuisance and you have to prove that too if you want to be reasonably certain of getting orders against the occupants and the owner.
At the very least, you will need a diary of when the noise occurs and what causes it. Backed up by recordings, statements of vistors to your home and the acoustic readings, you will have as strong a case as you can muster.