I see... yes these surveys started a while ago, before running firmware updates on the devices. Will send you the list soon. Thanks a lot for your help!

Yes, they were created using AudioMoth-Firmware-Basic (1.4.0). The AMs were deployed using the amplitude threshold but had the sleep cycle turned off, unfortunately. After switching date, the 2nd file probably got filled (?) and now gives trouble when trying to expand it. However, they do contain a lot of data, which would be even more useful if we could extract the time of detections. Ok, I'll send you the CONFIG.TXT and ERRORS.TXT files too. Thanks!

Thanks for your response Alex. Well, in this case the files were taken directly from the SD card (without resaving them with other audio applications). I didn't find any additional metadata at the end of the file using a hex editor. Sure, it would be great if you can take a look at one of them, is there an email where I can send you a link to the file?