Development of a low-cost hydrophone for research, education, and community science

Marine bioacoustics, the study of how marine organisms produce and are affected by sound, has become a cornerstone in ocean conservation efforts. Underwater microphones, known as hydrophones, can be used for ecosystem health monitoring, species distribution studies, impact assessment, anti-poaching and compliance, marine protected area management, climate change research and restoration efforts. However, the high cost and complexity of current autonomous hydrophone recording systems limit accessibility, particularly in educational and community science contexts, and in developing countries. Most autonomous hydrophone recording units are prohibitively expensive, exceeding US $3,000, while cheaper implementations lack the necessary recording and power supply characteristics, preventing cost-effective setup deployment of hydrophones.

Launched under the auspices of POGO (pogo-ocean.org) and the International Quiet Ocean Experiment (IQOE – iqoe.org), our Task Team on Low-Cost Hydrophones for Research, Education, and Citizen Science was created in 2023 to promote affordable hydrophone technology dedicated to research, education, and community science. Our project proposes to develop and test a low-cost, open-source, modular, and autonomous hydrophone recording system that breaks down these barriers, fostering innovation and broadening participation in marine research, conservation, and restoration.

Here, we present our prototype design, including hydrophone ceramics with a frequency response range from 10 Hz to 100 kHz and an effective sensitivity of -180 dB re V/uPa. It will be calibratable for accuracy and reliability in data collection. Our proposed data logger is based on an ARM Cortex M7 microchip that can handle sample rates up to 768 kHz and is designed for field use with longevity contingent on programmable settings.

We believe that the potential of aquatic bioacoustics is currently untapped due to the prohibitive costs and technical expertise required, confining its use to professional circles. By democratising access to this technology, we would like to unlock new opportunities for conservation efforts and uniform educational engagement worldwide.