With Loop Recording set to 3 minutes (default) and Time Lapse set to 100ms, Beep Sound set to Off, the unit beeps does a two double beeps every 3 minutes. (beep beep, pause, beep beep).
This occurred on firmware v1.60 and also the 17 June 2017 release V1.60.01B.
Beep Sound off means beep...