Dear all, I am as well recording NFC (with an Audiomoth 1.1.0) and also routinely catching bad calls at very low frequencies (below 10 kHz). In this case, they should probably be Pipistrelles, which call at 50 kHz or more. I guess it could be related with the signal processing of the device. Could you give some insight into this matter? Kind regards, Ferran Pujol