AudioMoth
Soundscapes to Landscapes
udioMoth is a low-cost, open-
source, full-spectrum acoustic
sensor capable of recording
uncompressed audio to a
microSD card for environmental
and biodiversity monitoring in
remote habitats. It was designed by Andrew Hill
and Peter Prince, two computer science PhD
students at the University of Southampton, along
with Alex Rogers, a computer science professor at
the University of Oxford.
These palm-sized devices are currently being
used to help researchers “move away from
passive continuous recording by individual, expensive
devices, towards using multiple low-cost, smart
devices that flood large and inaccessible
ecosystems,” says Andrew.
In addition to monitoring wildlife populations by
recording sounds made by target species at a
sampling rate of up to 384kHz, AudioMoth can also
be used to detect potential threats to protected
habitats by listening for poachers’ gunshots or the
sound of chainsaws used in illegal logging.GUNSHOTS AND CHAINSAWS
“Until now, professional ecologists typically had been
surveying wildlife with commercial equipment. The
cost advantage of AudioMoth completely changes
the science people can do,” says Alex. “Previously,
if an ecologist had a small budget, they could
maybe only deploy three or four recorders. Now
they can potentially deploy a hundred recorders,
meaning different types of wildlife surveys can
be conducted.”
The system is built around an energy-efficient
EFM32 Gecko 32-bit MCU, which includes up
to 128kB flash and 16kB RAM. It also
features an analogue MEMS microphone
(similar to the microphone inside your
smartphone) and preamplifier with adjustable
gain. Power is supplied by
three AA-cell batteries or an
external 6 V lantern battery,
while an RTC (real-time
clock) is used to keep anaccurate track of time for recordings scheduled using
the companion smartphone app.
The companion app also enables users to
customise the gain and sample rates, as well as
calculate the device’s approximate battery life with
any given configuration. The size of a fully assembled
AudioMoth is just 58 mm long, 48 mm wide, and
18 mm thick, which is slightly bigger than a box of
safety matches. This means that over a hundred
devices can fit into a standard 25 l capacity backpack.
“From the beginning, we were looking to create
a minimal device we could run smart algorithms on to
only record when hearing a sound of interest,”
explains Alex. “With the Gecko MCU, we can do
nearly all the listening while the processor sleeps,
then it can wake up to run the detection algorithms
across a four-second sound buffer.” This feature
makes it possible to deploy AudioMoths in the field
for up to twelve months, with each device listening
continuously for twelve hours per day.
“We have a lot of deployments in remote jungles
and forests with extremely limited internet access,
but we are still planning to add low-power wireless
connectivity to new versions of the device for alerting,
streaming, and research purposes,” adds Alex.A
FLYING
MAMMALS
The Bat Conservation
Trust is currently using
AudioMoth technology
to develop an automated
end-to-end system for
monitoring bats in
Britain. The system
includes an app that
enables volunteers to
send audio recordings
to a central server for
processing, algorithms
to automatically detect
and classify bat calls to
species, and an online
portal to share the
survey results with
volunteers and members
of the public. On top of
that, as much of the
technology as possible
will be open-source.meaning different types of wildlife surveys can
be conducted.”FEATURE
Left
An AudioMoth ready to
Ie depSo`ed in the fieSd
to gather important
acoustic dataAbove
The AudioMoth companion app can be used to schedule
recordings, customise the gain and sample rates, as well as
calculate the device’s approximate remaining battery life