Miniopteris australis ?
Distribution map based on Atlas of Living Australia
Overlaps in frequency with Vespadelus pumilus at 57 to 58 kHz, but most good calls can be distinguished by the presence of a down-sweeping tail.
This identification is not 100%. It is a possible Eastern Forest Bat, Vespadelus pumilus.
MausM00168, 121122 00:12:44 , Brunswick Heads, Google Earth
Here is the Miniopterus feeding buzz.
MausM00349, 121203 04:41:04, Brunswick Heads, Google Earth