Saccolaimus flaviventris SAFL
Distribution map based on Atlas of Living Australia
15-20 kHz often with harmonics. Actually, this is the dominant 2nd harmonic and sometimes you can see the first and third (in this recording) harmonic.
I have only recorded this bat in one single place, Brunswick Heads.

SflaM00527, 121205 00:55:07, Brunswick Heads, Google Earth