Testing the new AudioMoth detector
Posted in:
Bats, Biodiversity, Birds, Migration, Research, Surveys and Assessment, Technology
Date posted: 7 July 2018
Alar Ecology has just taken delivery of three new AudioMoth detectors and we have another three units on order! Our aim is to use these mainly for static/remote recording of bat activity at larger sites (the low cost of the AudioMoth makes it possible to deploy many units simultaneously), but other applications are possible – for example, the monitoring of nocturnal migration at bird-sensitive sites proposed for wind energy schemes.
In recent years there has been an increase in the popularity of ‘nocmigging’. This involves recording the nocturnal flight calls (NFCs) of migrant birds as they pass overhead, using a recording device and microphone. In just the same way as bat calls are recorded, bird calls can be saved to a memory card (AudioMoth uses micro SD) and subsequently analysed using proprietary software, including free products such as Audacity. An even more exciting development is the use of artificial intelligence (AI) to identify bird calls – although computer algorithms can’t outperform human, they can come pretty close!
According to Open Acoustic Devices (see the link below), AudioMoth is a low-cost, full-spectrum acoustic logger, based on the Silicon Labs Gecko processor range. Just like its namesake, AudioMoth can listen for sound from audible frequencies, well into ultrasonic frequencies. It is capable of recording uncompressed audio to micro SD card from 8,000 samples per seconds to 384,000 samples per second.
Key features of the AudioMoth are:
- EFM32 Gecko processor
- Capable of recording at sample rates up to 192kHz
- Experimental mode at 384kHz
- Records uncompressed WAV files to SD card
- Powered by 3 x AA batteries
- Analog MEMS microphone
- Analog pre-amplifier with adjustable gain
- Measures just 58 x 48 x 15 mm
- Configurable USB interface
- Onboard real-time clock keeps track of time in UTC
Unlike most other commercial detectors, both the firmware and software for the AudioMoth are open source (and programmable) and free to download. A detailed technical evaluation of the AudioMoth, including case studies, was published recently in the journal Methods in Ecology and Evolution (British Ecological Society). A full copy of the article can be downloaded here.
The AudioMoth has already been used for some big, high profile projects, revealing the global reach of this affordable technology. These include the following:
- RE-FINDING THE NEW FOREST CICADA | The New Forest cicada is the only cicada native to the UK. During May to July it sings with a very characteristic high-pitched song, which is at the limits of human hearing, and is particularly difficult for most adults to hear. Sightings of the cicada within the New Forest date back to 1812, but the last unconfirmed sighting was in 2000! That’s why a team of computer scientists from the University of Oxford and the University of Southampton have been deploying acoustic devices, called AudioMoth, in the New Forest, that can detect and recognise the song of the cicada, with the hope of rediscovering it in 2018 ( https://www.oxfordsparks.ox.ac.uk/content/where-have-all-cicadas-gone)..
- FIGHTING HUNTING AND ILLEGAL LOGGING IN SOUTH AMERICA | “One of the main objectives to develop AudioMoth was to design a new technique with which anthropogenic disturbances can be monitored, such as gunfire, which are often linked to illegal hunting of wildlife,” explains the biologist. Acoustic monitoring equipment recently developed by a team at the University of Southampton, in the United Kingdom … can record shotgun sounds and chainsaws, allowing researchers to discover frequency and patterns in the illegal exploitation of species (https://es.mongabay.com/2018/05/monitoreo-acustico-caza-tala-ilegal/).
- SEARCHING FOR ‘EXTINCT’ BATS IN CUBA | … the greater funnel-eared bat (Natalus primus) is special. Seen only as fossils, the species was thought to be extinct. In 1992, it came back from the dead.To find out where N. primus goes each night, we deploy dozens of sound traps in the forest – acoustic versions of camera traps, tuned to listen for and record the ultrasonic call of the species (https://www.newscientist.com/article/2130750-hanging-on-in-search-of-the-bat-that-returned-from-the-dead/).
Over the coming weeks and months, Alar Ecology will be carrying out tests on the AudioMoth, comparing the results with an Anabat Express which will be deployed in parallel. During October and November, we’ll also be looking at the ‘nocmigging’ capabilities of the AudioMoth, by targeting the arrival of wintering thrushes to SW England. Watch this space!
RELATED LINKS
Shuttleworth Fellowship … funding people who are unafraid to re-image the world and the way we live it.
Arribada Initiative … delivering affordable, open conservation technology for all.
… also [this blog article], about the AudioMoth … Driving down the cost of acoustic monitoring with the AudioMoth.
GroupGets …empowers users to securely launch or join group buys for any existing product.
Open Acoustic Devices … creators of AudioMoth, a low-cost, open-source acoustic logger for biodiversity and environmental monitoring.
GitHub … the world’s largest community of developers to discover, share, and build better software.
Audacity … Audacity is an easy-to-use, multi-track audio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems. Developed by a group of volunteers as open source.
Nocmigging … Listening [to birds] in the darkness.
Science Magazine … Watch out, birders: Artificial intelligence has learned to spot birds from their songs.
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