AudioMoth

audiomoth.jpgThe AudioMoth is new small recording device produced by Open Acoustic Devices. It has been designed as an autonomous recorder, so can be programmed to turn on/off on particular routines, and can be configured to record bats as well as birds. It takes 3 AA batteries and a micro SD card and can theoretically be left to run for several days (depending on sample rate and duty cycle). It seems to offer a lot for its £50–75 price tag. Its appearance is deceptive too. At only 50×60×20mm it’s tiny and its microphone is invisible under a tiny hole in the PCB. You’d think it can’t possibly compete with portable recorder and a shotgun or parabolic mic. But the results are surprisingly good.

Formal tests of AudioMoth have been undertaken (e.g. here) though we’re not aware of tests focused on nocmig capabilities. The spectrograms below are from a simple night test in March 2018 and show recordings of the same flock of Wigeon using the AudioMoth (top) and a parabolic mic (bottom). Gain on the AudioMoth was at its default middle position, and the parabolic mic set to 65% gain.  The AudioMoth did a decent job of picking up the birds when they were at their closest, but more distant calls were lost. Similar detection patterns were noted for near vs. distant Redwings. We are currently testing AudioMoths using higher gain settings (there are 5 in total) and will see how it performs when fitted in a parabolic dish.

AMvsPM_wigeon
A Wigeon flock recorded using AudioMoth (top) and a Dodotronic parabolic mic with Zoom H4n Pro recorder (Simon Gillings)

In autumn 2018 the developers of Audiomoth announced that they were developing a Mark II version which, among other improvements, would allow for an external powered mono microphone to be attached. This would solve the waterproofing issues and allow high sensitivity external mics (e.g. EM172 capsules) to be used. As soon as the Mk II becomes available we will post an update here.