A Low-Cost Passive Acoustic Toolkit for Underwater Recordings

Area of Science:

• Marine Biology
• Acoustics
• Environmental Science

Background:

• Passive acoustic monitoring (PAM) is crucial for studying marine soundscapes and human impacts.
• High costs of scientific hydrophones limit widespread PAM deployment and citizen science involvement.

Purpose of the Study:

• To design, build, and evaluate a low-cost hydrophone toolkit for accessible passive acoustic monitoring.
• To assess the performance of the low-cost system compared to calibrated scientific instruments.

Main Methods:

• Developed a hydrophone unit using off-the-shelf components (~20 €) paired with a handheld recorder (~50 € total system cost).
• Conducted field experiments in diverse Greek coastal environments (marine-protected area, port, aquaculture, reef).
• Compared recordings from the low-cost hydrophone with a calibrated scientific hydrophone (SNAP).

Main Results:

• The low-cost hydrophone system proved mechanically robust in field conditions.
• It consistently detected most anthropogenic sounds identified by the scientific reference hydrophone.
• Performance limitations were observed at low frequencies (<200 Hz) and mid-frequency resonance (3 kHz).

Conclusions:

• The low-cost hydrophone toolkit offers a viable, scalable solution for large-scale, budget-conscious passive acoustic monitoring.
• This system has significant potential for citizen science, educational outreach, and resource-limited research groups.
• Further development could address frequency limitations for broader applications.