I use μMoth to record bats.
With the sampling frequency at 384 kHz I always register regular disturbing signals. If I lower the sampling rate to 250 kHz it doesn't happen to me.
It looks like a disturbance produced by the micromoth
I attach sample files.
Thanks for suggestions
Paolo Debernardi
SanDisk Ultra might also be a bit slow for 250 and 384kHz recording. Most LiPo batteries will give good performance. Be a bit wary of powering the uMoth (or AudioMoth) through the USB socket. It will work okay but the 5V supplied by the USB can be quite noisy. It depends a lot on the power pack or computer.
Thanks Alex,
I try to change cards (I used SanDisk Ultra cards) and improve the power supply.
Paolo
The regular vertical bands about every 40ms are caused by the physical noise of the SD card write occurring. It's one of the consequences of the small design with the SD card on the same board as the microphone. Some SD cards are a bit noisier than others (we use SanDisk Extreme cards) and it will be a bit more noticeable as the battery voltage decreases.