On scanning older (2019) Audiomoth recordings my software has picked up 3 instances of strange 9-second long almost pure 600hz tonal sounds that the ornithologists and other experts I have consulted cannot identify. Looking at the spectrograms I'm starting to wonder if they are generated within the unit itself such as a defrag of the SD card or something like that. Any ideas?
Early and late in the day but just diurnal. Barmah Forest Victoria on the Murray River. Interesting isn't it?