Conclusionsīased on these recordings the AudioMoth with external mic showed some small improvements on the AudioMoth in the case, though they weren’t as significant as I was expecting. Again the AudioMoth with external mic shows a small but significant improvement on the device in the case. The AudioMoth with external mic is almost on a par with the right channel of the Dodotronic, and noticeably better than the device in the case. This bird was off to the left of the garden as evident from the Dodotronic channels where the call is much stronger on the left channel. Little Grebe recorded using Dodotronic parabolic mic, SM4mini, AudioMoth with external EM272 mic and AudioMoth in a standard case Robin Ī single Robin flight call, visible on all recordings, but with detail slightly variable across the recordings. I suspect I might have missed this call entirely on the recordings from the AudioMoth in the case. The AudioMoth with external mic is definitely an improvement on the device in the case, but still inferior to the Dodotronic and SM4mini. The upper harmonic was invisible on both AudioMoth recordings. Little Grebe Ī pair of Little Grebe ‘scream’ calls. There is some marginal improvement with using the external mic. The note is identifiable on all equipment but weaker in the AudioMoths. Note that the recordings made with a parabolic reflector may not show a major improvement over those without a reflector if the bird was outside the main receptive zone in front of the reflector. In each of the following images the spectrograms are in the order Dodotronic (both channels, or just the strongest), SM4mini, AudioMoth with external mic, AudioMoth in box. I think this shows how easily a call recorded on the different gear would be detected by a human observer. Instead, as for most casual nocmig purposes we visually check spectrograms to detect calls, I have just produced standard spectrograms as they would appear when processing a recording. I haven’t done any formal measurements of signal strength. In the foreground the EM272 mic in a parabolic reflector in the background, left to right, the AudioMoth unit with the external mic plugged in, the AudioMoth in standard case, and the SM4mini. Three of the devices used in the comparison. AudioMoth in a standard AudioMoth case gain set to medium.I crudely sealed the hole by wrapping a strip of an old bike innertube around the cable. The AudioMoth was put inside a small cliplock food storage box with a hole drilled in the end for the cable to exit. AudioMoth with EM272 external mic in a parabolic reflector gain set to medium.Wildlife Acoustics SM4mini, set to 24dB gain.Dodotronic Hi-Stereo parabolic mic recording to MixPre3 recorder, set to 28dB gain.To field test the AudioMoth with external mic I ran the following equipment side by side over 2 nights in February 2021: They come with a decent length of cable so can be routed into a parabolic reflector if required. I opted for a Primo EM272 capsule mic as these are affordable and good quality. you don’t need to enable anything in the Configuration App. To use an external mic you simply plug it in – i.e. It is clearly stated on the OpenAcoustic’s website but worth reiterating that once you have attached the audio jack, the device will no longer fit in the standard AudioMoth case. It’s a bit fiddly, but even with my limited soldering experience I managed to do it OK. The external 3.5mm jack does not come fitted and has to be soldered onto the six contacts on the top of the unit.
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