Triggered & continuous recordings comparability
Hi everyone,
I would like to compare recordings made with an amplitude trigger (and high pass filter) to continuous recordings without any filters for a monitoring project. I think the only way to get some comparability would be to apply some kind of filter to the continuous recordings that emulates what the AudioMoth firmware does during triggered recordings. This way, the continuous recordings can be transformed into "triggered-like" recordings, which can then be compared to regular triggered recordings.
I already had a look at the firmware source code, and it seems quite doable to implement such a filter. But before I sink any time into actually doing this I wanted to ask if anything like that has already been done? I haven't found anything when searching the forum.
Cheers,
Jaro
Hi Jaro, Yes. The filter is applied first, and then the triggering uses this filtered output, writing it to the SD card in 32KB chunks whenever it is above the threshold. For your comparison you can probably just apply the filter and save the filtered file. You can also experiment with the trigger settings in AudioMoth-Play to compare their effect. The butterworth.js file in AudioMoth-Play will allow you to apply the same filter that AudioMoth uses. For node.js also have a look at AudioMoth-Utils (https://github.com/OpenAcousticDevices/AudioMoth-Utils) which provides some code for reading and writing WAV and GUANO headers. The splitter.js file is probably a good starting point as it correctly reads and updates the header and GUANO meta-data. You can just add the butterworth.js code to apply the filter to the data that is read from the original file.
Alex