Audio | Info on Bats | AudioMoth
Open Acoustic Devices is a small, UK-based research group formed from a collaboration between the University of Southampton and Oxford University. We design, support and deploy open-source acoustic hardware and software for our user community, as well as our own environmental and wildlife monitoring projects.
Our main research contribution is AudioMoth, which has been used in multiple applications, including automating the search for an elusive insect species, monitoring poaching by gunshot and listening for ultrasonic bat calls.
Our goal is to improve the accessibility and usability of acoustic technology for conservation using open-science.
" Cost-effective bat detectors - AudioMoths
Posted by Barry S on 11 September 2019 12:35pm
Hi All,
AudioMoths (https://www.openacousticdevices.info/) have been mentioned in recent posts by Damian and Leroy. AudioMoths are cheap (circa AU$100 ea) broad-spectrum bioacoustic recorders that sample ultrasound too. The UK BatConsTrust conducts the National Bat Monitoring Programme using these. I’ve recently acquired four mainly for night/ground parrot surveys with Mike Bamford. I ran one side by side with an SM4BAT FS for a couple nights. The AudioMoth obtained all the Chal gouldii calls recorded by the SM4BAT, and more but only of poor quality records which were ignored by the SM4BAT auto detection.
AudioMoths record constantly (according to a schedule/calendar) rather than per detection so you have more data to store and analyse. Storage is eaten up relatively quickly compared with the selective recording of more sophisticated units. Sampling between 19:00 and midnight, the AudioMoth will generate 4.4 GB/evening at 192 kHz sampling rate, 5.8 GB at 256 kHz and 8.7 GB at 384 kHz. This gives between 7 and 14 nights of sampling on a 64GB card. Remarkably, three rechargeable AA batteries will last for 25+ days, though Lithiums will go longer (but are throw-away). Investing in bigger cards is easy since you save so much on the recording unit. The signal/noise ratio is not as good as the SM4BAT (with old mic) (see attached sonograms of same sequence) so analysis using zero crossing isn’t quite as effective but isn’t dismal. AudioMoths aren’t field hardened like the SM4BATs and need careful handling. You also need to make a waterproof housing (per Leroy's post - see CanConsTrust).
Most importantly, AudioMoths now give us the ability to saturate a sampling area with detectors. This gives us way-better detection potential for the rarities and a previously cost-prohibitive means of assessing landscape ecology and estimating bat abundance. I'm intending to trial an abundance estimation method on an island near Perth which offers an effective closed population.
Upshot is for $100/AudioMoth (minus batteries and micro-SD) compared with $1000/for a mainstream static detector (minus batteries and card), you can do an awful lot more. Downside is a lot of data are generated. Assuming the auto-detection methods work, and they should, there isn't a downside.
Barry"
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