Hey friends! I'm attempting to record bat calls throughout the winter. I've been having issues with having large WAV files that Sonobat does not like to open. I will often have many small files in a night (anywhere from 41 kB to 8,000+ kB) and Sonobat has no problem opening and viewing those. However, I will often have WAV files up to 26,000 kB and I am unable to view them in Sonobat at all. This is quite discouraging, as I believe these files could contain bat calls (as well as a lot of noise) and I have quite a lot of these files that are "too large" to view (in Sonobat anyway). Below are my settings:
Sample rate: 250 kHz
Gain: Med
Enabled sleep record cycle: Sleep 5, Record 55
Filter type: High (recordings filtered to freq above 16.0 kHz)
Enabled amplitude threshold recording: 512
Additionally, I have many sites along streams and those sites especially produce large files (sometimes ALL the files are 26,000+ kB and therefore unviewable in Sonobat). I believe this is due to the sounds from the rushing water. Does anyone have any suggestions of how to filter out the water? I'd like to be able to capture bats as low as 16.0 kHz if possible (such as Lasiurus cinereus). Perhaps the only way to filter out the water would be to increase the filter? But has anyone had any luck by increasing (or decreasing) the amplitude threshold recording settings around water? Would changing the gain help?
Any insights or tips would be extremely helpful! Thanks in advance!
I don't know about Sonobat but most audio applications will have no problem opening these files. Amadeus Pro opens WAV files up to 4.3 GB in size.
The red LED will only flash while it is actually writing to the SD card. You can set the amplitude threshold experimentally by increasing it a little until you don't make continuous recordings. If you rub you hands together a few meters away from the AudioMoth you normally generate enough ultrasonics to trigger a recording.
Sadly, I don't. The issue is that I can't even open a lot of my files to see if they contain bat calls because they are too "large" for the WAV file viewer I'm using (Sonobat). Do you know of any other WAV file viewers that would be able to view 26,000+ kB files?
Thank you for the recommendations though! I will definitely test out both increasing the amplitude threshold and increasing the filter cut-off frequency (in separate trials). The good news is that we are getting bat calls, but the large number of these unviewable files is a bit concerning!
Do you have an example recording which shows both the background noise level and a bat call? Either increasing the filter cut-off frequency or the amplitude threshold will make the recordings more specific to the bat calls. The filter is a first-order Butterworth filter which doesn't have a very sharp frequency response, and bat calls are generally very loud, so you will still be able to record bat calls at or below the cut-off frequency.