The extractor fans are a common property issue and if they are keeping you awake at might they clearly haven’t been installed with any consideration of the disturbance they may make.
Write to your Owners Corporation secretary and demand (politely) that the noise levels be investigated and remedied.
If they refuse or do nothing, count down the two weeks specified in the law then pursue your rights under section 232 of the Act to compel them to fulfil their obligations to maintain and repair common property. You would do that by first applying to Fair Trading for mediation then taking your issue to NCAT.