Field-based Testing of Sound Reception by Autonomous Recording Units- AudioMoth, SongMeter4, and SoundCache (October 2018)

Playback was used in real-world field conditions to test relative sound capture by three autonomous recording unit types: AudioMoth, SongMeter4, and SoundCache. Testing was performed at wetlands within the City of Calgary, under appropriate municipal and provincial permitting. Devices were tested using 11 stimuli standardized to 85dB peak amplitude at a variety of distances. Stimuli included artificial simplified sounds (1khz tone, 5khz tone, 10kHz tone, and broadband white noise), amphibians calls (western toad, northern leopard frog, Canadian toad), and bird song (common nighthawk, bobolink, olive-sided flycatcher, and Canada warbler). These stimuli were chosen to represent a diversity of acoustic characteristics including a variety of frequencies within the audible range, and frequency modulation (tonal, narrow frequency sounds to broadband buzzy sounds). Device settings were adjusted to match were possible (48kHz sampling rate, 16-bit wav files), and held at factory settings when the metrics were not comparable (e.g. gain settings). Recordings were reviewed in Audacity 2.1.3 and stimuli were marked "captured" when a sound was visible on the spectrogram or audible in the recording. No quality metrics were applied, this was a simple presence/absence test.