Kleinvoet: a Spatially-Distributed Temporally-Synchronised Infrasonic Recorder

We present the hardware design of a high-fidelity, low-cost infrasonic-capable (6 Hz) passive acoustic monitoring (PAM) prototype instrument. The device allows temporal synchronisation using a variety of global navigation satellite system (GNSS) constellations. This allows the recordings made by independent spatially-distributed nodes to be synchronised in time for acoustic monitoring and localisation using, for example, time difference of arrival (TDOA). Each node is capable of sampling at 24-bit resolution with a sampling frequency that is adjustable between 8 kHz and 192 kHz. Audio samples are stored locally on a microSD card, along with timestamp and location metadata.