Using Passive Acoustic Monitoring to Track Human Activities Underwater
Passive Acoustic Monitoring (PAM) has become an important technology for observing human activities in underwater environments. It provides a non-invasive means of tracking sound and understanding its impact on marine ecosystems. By recording and analyzing the various sounds generated underwater — both natural and human-made — PAM offers valuable insights into how human presence affects oceanic life. Whether monitoring shipping lanes, detecting illegal fishing activities, or assessing the impact of underwater construction, PAM serves as a key tool in sustainable ocean management.
In this article, we would like to give more detail on how PAM is used to monitor human activities underwater, and why it is essential for protecting marine environments.
Passive Acoustic Monitoring Explained
Passive Acoustic Monitoring is a technique that uses hydrophones (underwater microphones) to listen to the sounds present in aquatic environments. Unlike active sonar systems, which send out sound pulses and detect their echoes, PAM is entirely passive; it only records sounds that naturally occur in the environment. This makes it especially suitable for monitoring sensitive marine habitats without introducing additional noise.
By using PAM, researchers can detect and analyze a wide range of underwater sounds, including the movement of ships, drilling operations, and other human activities that generate noise. This data can be used to assess how human-generated sounds affect marine life, monitor compliance with regulations, and identify unauthorized activities in restricted waters.
How Does PAM Monitor Human Activities Underwater?
PAM systems designed for monitoring human activities underwater typically consist of several components:
Hydrophones.
These devices capture underwater sounds across a broad spectrum of frequencies, making them capable of detecting both low-frequency noises, like ship engines, and high-frequency sounds, such as those produced by certain marine species.
Data Storage and Transmission.
Audio data recorded by the hydrophones is stored locally or transmitted to remote servers for further analysis, depending on the deployment strategy.
Analysis Software.
Specialized software analyzes the recorded sounds, distinguishing between different sources — such as a fishing boat engine versus natural sounds like whale vocalizations.
Reporting Tools.
The analyzed data is then used to generate reports, monitor trends, or trigger alerts for specific events, such as the presence of illegal fishing vessels.
The effectiveness of PAM relies on the placement of hydrophones, which must be carefully positioned to capture the relevant sounds. In regions with heavy ship traffic or industrial activities, hydrophones are often deployed near shipping lanes or close to construction sites to monitor the extent of noise pollution.
Applications of PAM in Monitoring Human Activities Underwater
PAM's ability to continuously record underwater sounds makes it a reliable tool for monitoring a variety of human activities that impact marine environments. Here are some key applications:
Monitoring Shipping Traffic
With increasing global trade, shipping traffic is a major source of underwater noise. Large vessels produce low-frequency noise that can travel long distances underwater, potentially disturbing marine life, particularly species that rely on sound for communication and navigation, such as whales.
PAM systems can track the movement of ships through their acoustic signatures, allowing researchers to study how noise levels change in key habitats. This information helps to identify areas where marine mammals may be affected by vessel traffic and can inform decisions on establishing shipping lanes or speed restrictions to minimize noise pollution.
Detecting Illegal Fishing and Poaching
Illegal fishing and poaching pose significant threats to marine ecosystems, especially in Marine Protected Areas. PAM can detect the sound of engines from unauthorized vessels, making it a valuable tool for enforcement agencies.
By recognizing the unique acoustic signatures of different types of vessels, PAM systems can alert authorities when suspicious activities are detected in restricted areas. This allows for quicker response times and more effective protection of marine resources.
Assessing the Impact of Offshore Construction
Offshore construction projects, such as wind farms, oil and gas drilling, and subsea cable installations, generate considerable noise that can disrupt marine life. PAM is used to monitor the acoustic environment around these sites before, during, and after construction to assess the impact of noise on local marine populations.
Hydrophones can be placed near construction sites to capture the sounds produced by pile driving, drilling, or cable laying. The collected data helps determine whether noise levels are within acceptable limits and provides insights into how marine species respond to these disturbances, guiding strategies to mitigate impacts.
Monitoring Seismic Surveys for Oil and Gas Exploration
Seismic surveys, which use powerful airguns to map subsea geology, generate intense sound waves that can impact marine life, particularly whales, dolphins and porpoises. PAM systems can track these activities, helping to ensure that surveys comply with environmental regulations that require companies to minimize noise exposure to marine mammals.
By continuously monitoring the area around seismic survey operations, PAM helps ensure compliance with mitigation measures, such as temporary shutdowns if marine mammals are detected nearby. This helps to balance the needs of energy exploration with the protection of vulnerable species.
Benefits of Using PAM for Monitoring Human Activities Underwater
The use of Passive Acoustic Monitoring for tracking human activities underwater offers several advantages. Firstly, PAM provides a way to observe underwater activities without interfering with marine ecosystems. This is particularly valuable in sensitive habitats where physical presence could disturb wildlife. Secondly, continuous data collection. PAM systems can operate around the clock, capturing data even in harsh weather conditions or remote locations where human observation is difficult. Thirdly, some PAM systems are equipped for real-time data transmission, enabling immediate responses to detected activities, such as the presence of unauthorized vessels in protected areas.
PAM can be adapted to various underwater environments, from shallow coastal regions to deep-sea habitats, making it suitable for a wide range of monitoring needs.
Future Trends in Underwater PAM
As technology advances, new developments are enhancing the capabilities of PAM systems for monitoring human activities underwater.
Integration of PAM technology with AI and Machine Learning
The use of AI in analyzing acoustic data helps to automate the identification of sound sources, reducing the time and effort required for analysis. This allows PAM systems to detect specific types of vessels or construction activities more accurately.
PAM Enhances Real-Time Communication
Improvements in underwater communication technologies are making it possible for PAM systems to transmit data in real time from remote areas, enabling more immediate decision-making.
PAM Can Be Deployed in Collaborative Monitoring Networks
Increasingly, PAM systems are being deployed as part of larger collaborative networks, where data from multiple hydrophones is combined to provide a comprehensive picture of underwater noise levels over a wide area.
Passive Acoustic Monitoring is a critical tool for understanding the impact of human activities on underwater ecosystems. By providing real-time data on shipping traffic, illegal fishing, and industrial noise, PAM helps researchers and regulators make informed decisions that balance human activity with the need to protect marine life.
As oceanic activities continue to expand, the role of PAM in ensuring sustainable marine management is more important than ever. It offers a powerful means of monitoring the health of our oceans while supporting conservation efforts and compliance with environmental regulations. With continued innovation and adoption, PAM will remain at the forefront of efforts to safeguard marine ecosystems from the growing pressures of human activities.