I'm new to recording bat sounds and working with the Audiomoths and i am trying to figure out the best settings to record bat flight and feeding activity. I got advise on the settings from people who worked with them previously to maximise the battery life, since i want them to record for about two weeks.
So far i have the settings on 192kHz with medium gain. Recording from 21.30 to 5.45 with a high pass filter at 16kHz and an amplitude threshold of 2048. These settings seem to be working fine, but i'm unsure about the sleep/record schedule.
I have played around with two AMs with different cycles; one on a 10s/5s and one on a 50s/5s record/sleep period. In the first case i had around 3000 files of very short recording (max 3 seconds), whereas the second had about 1000 files up to 8 seconds long. Both recorded during two nights. With both settings there seemed to be only one recording per record cycle. How does this work when there are two seperate instances of bats passing during a long recording period? Does this produce multiple files or does it combine the recordings into one longer file?
I have seen people use 4minute/1minute cycles or even 1h/5s cycles and cases where they use 10s/5s. I assume it differs a lot depending on what type of activity you want to record but i'm curious about the pros and cons of such schedules.
The long recording periods must be taxing for the battery life. Since i want them to last for 2 weeks this might not be the best option. However, the massive amount of small files isn't ideal either.
I will be recording in an area with few bats, so in case a bat passes I dont want to miss it due to a long sleep period. Additionally, I have heard that a short sleep period (1s) can cause problems where the file isn't properly saved.
Thanks in advance for any advise on this topic!
Great. We normally end up with T.WAV files that are about 1/20 to 1/100 of the size of the equivalent continuous WAV recording depending on how many bats come past and if the AudioMoth has triggered on other background sounds. Reducing the amount of data that is written to the SD card also yields quite a significant energy saving.
Thank you for your reply! Mine is a bit late, but it was very helpful. I have tried the settings you suggested and ended up using the 10 minute cycle and an amplitude filter of 1024. I set the frequency filter to 20 kHz. There wasn't much trouble with background noise and I worried that a 40 kHz filter would remove bat species with lower frequency calls.
These settings lasted for at least 12 nights so far with lithium batteries, and very active bats.
I noticed that expanding the file significantly increased the size. This is not a problem for me, but might be good to know if that is a restriction.
Yes, that would work. It depends what sampling rate you are using but 1 hour recordings are only 300MB at 48kHz so splitting those will be pretty fast.
thank you for the incredibly fast reply!
I did not discover that function in the configuration app yet, thank you very much!
Would you then recommend, like for Alrike, to record 9 min 55 sec out of 10 min and split these files into 1 min? I remember that with other acoustic recorders handling long recordings later on my laptop got tricky or slow.
Hi Saskia, It normally takes about 2 seconds to close and open a new file, so you can use the sleep/record option, but you will always have short gaps between the files. To avoid the gaps you can record longer periods and then use the 'Split AudioMoth Recordings' option in the Config App to generate the 1 minute recordings.