Solo: an open source, customizable and inexpensive audio recorder for bioacoustic research

Audio recorders are widely used in terrestrial and marine ecology and are essential for studying many cryptic or elusive taxa. Although several commercial systems are available, they are often expensive and are rarely user-serviceable or easily customized. Here, we present the Solo audio recorder. Units are constructed from the Raspberry Pi single board computer and run easy-to-install and freely available software. We provide an example configuration costing 167 (83 pound excluding suggested memory card and battery), which records audible sound continuously for c. 40days. We also provide a video tutorial showing hardware assembly and documentation is available via a supporting website. The Solo recorder has been extensively field tested in temperate and tropical regions, with over 50000h of audio collected to date. This highly customizable and inexpensive system could greatly increase the scale and ease of conducting bioacoustic studies.