I plan to use one of my AudioMoth for on-side non-stop recordings (Going on-side, use audio-chime to switch it on, leave it there for multiple hours and then come back and turn it off).
I am unsure how and when the audio files are written to the sd-card. Is the current file still written before it turns off or is there a danger to lose the entire recording if it is shut off while recording. Furthermore, Is the file split on longer recordings or will it be one giant file?
Thanks for the clarification! That helped a lot
Each audio files is written continuously to the SD card but in order for the file to be readable it has to be closed correctly. If you switch from CUSTOM back to USB/OFF then the AudioMoth will safely stop the recording and close the file. You will then be able to read it. The WAV header comments will say that the file was stopped due to the switch position changing. If you remove the SD card or batteries, the file won't be closed and won't be readable (although the data is still on the card and can be recovered with a bit of work). For this reason, we normally advise to write one hour recordings with short 5 second gaps - use recording time of 3595 seconds and sleep time of 5 seconds. This will give you one hour (minus 5 second) recordings which start on the change of the hour. When you switch to CUSTOM the first recording will start immediately.
WAV files have a maximum size of 4.3GB so if you have a high sample rate, and disable sleep/record cyclic recording, the AudioMoth will automatically limit the file length to stay just under this limit. However, this means that the file start times will not be so systematic.