FAQ

An AudioMoth is not a commercial product and the cheapest way to get one is when a buying round is open on GroupGets.  GroupGets are selling AudioMoths with a $20 premium

A buying round on GroupGets is limited to a specific number e.g. only 600 available, this is because there is a limited supply of components available - so in general a round cannot be increased.  In early 2019 a buying round was closed early because the number of units exceeded the time allocated to manufacture, these little units are getting mighty popular!  It now appears that GroupsGets buying rounds are almost continuous.

AudioMoth uses a MEMS microphone which is surface mounted, a close look at the board shows a microphone picture with a small hole.  This is the entrance for the sound.

The microphone is surfaced mounted into the board and the board is designed to work that way, there was no facility for an external/remote microphone however the latest version has a bare header for a 3.5mm jack to run an external microphone.  Note: the jack is not supplied so you need to solder on your own.

You select the recording frequency by selecting the sample rate, so a sample rate of 384Kbs translates to a Frequency of 0-192Khz - the downside is you will need to ensure the microSD card is fast enough to accept the data ie Class 10 U3

There is an issue with version 1.0 builds as the slider select switch sticks out from the board and can be damaged.  The good news is that the project has redesigned the board (version 1.1) so the switch is slightly recesses . 

The slider in the switch body can be replaced and the switch you need is a Nidec Copal CSS-1310TB, see the AudioMoth Forum for a pinned post on Simple Switch Repair.

The microphone is a Knowles SPM0408LE5H-TB-6 microphone.   Datasheet

There is an updated version of firmware and apps - all the instruction are on the AudioMoth site - however if the file gets corrupted before or during the upload the AudioMoth will brick* and need to be recovered - the instructions from Peter Prince are:

If the firmware got corrupted you won't see the flashing LED as per the instructions and the device is probably going straight to sleep as it can't find any firmware to run.

The way around this is to remove the batteries, hold the paperclip onto the contacts, and then plug in the USB cable - a third hand is useful here. That way the device powers up and immediately finds that it should be in bootloader mode.

*brick or bricked is the term used when a device has failed and is as "useful as a brick" :)

also ensure the paperclip is not lacquered better to use a piece of solid copper earth wire bent into a U shape.

There has been a lot of talk about batteries and longer life.  The unit can be powered via a USB 5v battery pack or you can clip an external battery/batteries on to the battery holder as long as the voltage is between 3.4 and 20 volts.

If the available voltage drops to 3.3v or below the unit can not write to the SD card.  Which is why rechargeable AA batteries do not always work very well - even when fully charged the voltage is quite low and quickly drops during discharge - so if you wanted to use rechargeables then I'd think about putting in a battery holder for 4 AAs.

If you want to get serious there is a project housing to power with a 6v lantern battery (PJ996 / 4R25) - see this paper for details

https://eprints.soton.ac.uk/432474/2/1_s2.0_S2468067219300306_main.pdf 

Below are the microphone sensitivity pattern (originally posted on the AudioMoth Forum)