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?
@Alex Rogers, Yes it is quite possibly real but I didn't want to hassle any other experts if I was chasing a hardware ghost. I have this at 3 different sites and I assume different Audiomoths as they were out for the one project. I have no idea what the SD cards were. It only occurs once each site and I can't find other calls around it in other files taken earlier or later that day (thus far) so maybe it moves on. I'd love to ID it as I'd put it in my database of sounds and use them as training. But I need a label.
Can you post an example of the WAV file. I don't think these are generated by the AudioMoth itself as nothing stops and starts in this way. The SD card itself may be doing something, but that seems unlikely. They often do some internal load balancing, but that typically just means that the physical and logical pages are switched around to ensure that the physical pages are used equally. What make and model SD card is this? I'd suspect a real external sound.