What is Passive Acoustic Monitoring?

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what is passive acoustic monitoring

Passive acoustics involves listening for sounds, usually within certain frequency ranges or specific analytical settings. One common use of this method is in Passive Acoustic Monitoring (PAM), where acoustic sensors are used to record animal and environmental sounds. Considered a crucial tool for the maritime area, PAM acts like a silent watcher, providing precious knowledge about underwater environments without disturbing the creatures living there.

From species detection to technological advancements, learn about the multifaceted role of this tool, its application, and its significance in environmental protection.

The Role of PAM in Species Detection

Within marine science, PAM known as acoustic monitoring serves as a valuable tool for species detection in aquatic ecosystems, offering researchers an efficient means of studying biodiversity. By leveraging the natural vocalization of the environment, the tool contributes to the understanding of species distribution, behavior, and ecological relationships

How is it used for species detection?

The Passive Acoustic Monitoring is gentle on the environment because it doesn’t disturb the marine animals. Named ‘acoustic’ because it records ambient environmental vocalizations. Researchers use the system to record ambient noise levels in various habitats, including forests, oceans, and urban areas. Here is how this non-invasive technique is used to detect sea creatures:

Marine mammals

One primary application of this device is the surveillance of marine mammals such as whales, dolphins, and porpoises. These animals produce a diverse range of vocalizations, including clicks, whistles, and songs, which can be detected and analyzed using the technology.

Aquatic animals

Acoustic monitoring is also valuable for detecting other aquatic organisms, such as fish, crustaceans, and marine invertebrates. Many of these varieties generate distinct sound recordings during activities such as courtship, feeding, and territorial defense.

Benefits of acoustic monitoring over traditional methods

The advantages of PAM over traditional approaches make it a valuable tool for studying and supervising marine life, facilitating conservation efforts, and informing sustainable management practices. The effective technique of supervising wildlife has significant advantages that set it apart from traditional techniques:

Non-invasiveness: The system allows researchers to oversee organisms without disturbing their natural behaviors or habitats. Unlike traditional methods such as visual surveys or trapping, which may involve handling or direct observation of animals, the device relies on remote sensing through sound detection.

Cost-effectiveness: Acoustic monitoring can be more cost-effective, especially for supervising species in remote or challenging environments. Once deployed, hydrophone arrays can collect data autonomously, reducing the need for extensive fieldwork and manpower. 

Species-specific detection: The technology can be tailored to detect specific breeds or groups of interest based on their unique acoustic signatures.

Data integration and analysis: The files can be integrated with other techniques, such as satellite imagery or oceanographic data, to provide a comprehensive picture of ecosystem health and biodiversity.

Species detectable through acoustic monitoring

The versatile equipment enables the detection and observation of various species across different habitats. From the depths of the ocean to the dense forest, the device allows researchers to capture the vocalizations of diverse organisms. Here are some examples of species that can be detected using PAM:

Marine mammals: Passive Acoustic Monitoring is frequently utilized to detect the presence of marine mammals, which can be challenging to observe from the surface. The common animals include whales, seals and sea lions, porpoises, dolphins, manatees and dugongs, and polar bears. Through their vocalizations used for communication and social interactions, the researchers can identify and oversee them. They can a sampling technique to collect samples at various locations, recording sound figures and rates of occurrence over different dates.

Birds: Many bird species are known for their distinctive calls and songs, which serve various purposes such as communication, mate attraction, and territorial defense. The number of animal vocalizations detected in recorded samples can provide an understanding of species diversity and abundance in each area.

Insects: While less commonly studied compared to marine mammals and birds, insects also produce sound signatures for communication and other purposes. Certain insects, such as crickets, katydids, and cicadas are known for their characteristic chirping or buzzing vocalizations.

Fish and other aquatic creatures: In addition to larger animals like marine mammals, it can also identify vocalizations produced by fish and other aquatic organisms. Fish produce a variety of sounds for communication, navigation, and prey detection, which can be recorded using underwater hydrophones.

Techniques and Tools with Data Associated

PAM involves the deployment of recording devices, such as field recorders, to capture an audio sample of environmental noises. It also can be utilized to study the effects of wind on transmission in open environments, such as grasslands or deserts. For example, the distribution of North Atlantic right whales in Canada from 2015-2017 was a study project that used the technology to track the presence and movements of North Atlantic right whales in Canadian waters.

Description of the tools and equipment

The primary advancement used in PAM is the hydrophone, which is an underwater microphone designed to detect signals in aquatic environments. Hydrophones come in various configurations, including omnidirectional and directional models, depending on the specific needs and environmental conditions. Some advanced tools also feature real-time surveillance capabilities, allowing researchers to remotely monitor and analyze acoustic files. To deploy hydrophones and recording devices in the field, researchers often use specialized equipment such as underwater housings, cables, and buoys. Once the sound recordings are collected, they must be processed and analyzed using specialized software and computer algorithms.

Types of data collected

In acoustic monitoring, two primary forms of data collected through the equipment include audio recordings and spectrograms.

Audio Recordings:

The systems capture audio recordings of environmental sounds using hydrophones. They encompass a wide range of vocalizations, including marine mammal vocalizations, anthropogenic noise (such as shipping and industrial activities), natural ambient sound patterns, and geological or hydrological events (such as earthquakes or underwater volcanic eruptions). These recordings are stored in digital formats in a database and can cover extended periods, allowing for continuous overseen and analysis.

For example, the pressure exerted by passing ships was calculated at specific sampling locations, aiding in understanding the impact on marine life.


They are graphical representations of sound frequencies and intensities over time. Generated from audio recordings, spectrograms provide a detailed visual depiction of acoustic signals, enabling researchers to analyze specific features such as frequency content, temporal patterns, and amplitude variations.

Innovations in Passive Acoustic Monitoring

The passive acoustic has become crucial in observing cetaceans, especially deep-diving marine fauna. It is also used to reduce negative impacts of human activities including maritime traffic and oceanic exploration. As PAM continues to grow in significance within the shipping industry, it has embraced innovations to enhance its effectiveness:

  • One major advancement lies in sensor technology, particularly in hydrophone design, which has seen continuous improvements. This results in more sensitive and reliable sensors capable of capturing underwater sound recordings with greater precision.
  • Recent advancements in machine learning and artificial intelligence (AI) have revolutionized species detection capabilities in PAM. Google’s AI algorithms were employed to analyze the data, revealing patterns in sound figures and rates over time.
  • AI algorithms can analyze large volumes of files and automatically detect and classify species vocalizations with high accuracy, reducing the need for manual analysis and speeding up data processing.


The roles of Sinay in PAM for automated species detection

Sinay, an advanced software platform, is integral to PAM for automated organism detection as it processes large volumes of sample data and enhances signal clarity through sophisticated algorithms. The company operates in real-time, continuously analyzing incoming data streams and enabling immediate species detection and classification.

Leveraging machine learning and artificial intelligence techniques, the start-up specialized in maritime data solutions automatically detects and classifies species vocalizations within the acoustic files. Sinay uses advanced pattern recognition algorithms to identify characteristic features in species vocalizations, facilitating accurate identification.

Development of specialized software and algorithms for data analysis

The development of specialized software and algorithms for PAM data analysis has significantly enhanced the field. These tools offer advanced features for signal processing, spectrogram evaluation, and pattern recognition, enabling researchers to figure out useful perceptions from recorded acoustic signals. They facilitate efficient data processing and interpretation, contributing to a deeper understanding of marine ecosystems.

Passive acoustic monitoring stands as a crucial tool in environmental studies, offering valuable insights into biodiversity, anthropogenic impacts, and ecosystem health. From species detection to understanding human influence on wildlife, PAM’s multifaceted role contributes to conservation efforts and sustainable management practices. As technological advancements continue to enhance its capabilities, innovation remains indispensable for vigilance and protecting our oceans’ delicate ecosystems.

Frequently Asked Questions About Passive Acoustic Monitoring

Passive acoustic monitoring (PAM) is a non-invasive technique used in marine biology to study underwater soundscapes and the behavior of marine organisms. It involves deploying hydrophones to passively record sounds emitted by marine species such as whales, dolphins, and fish without disturbing their natural habitat.

Passive acoustic monitoring (PAM) plays a crucial role in ocean conservation efforts by providing valuable insights into the distribution, abundance, and behavior of marine species. By analyzing the acoustic data collected, scientists can assess the impacts of human activities such as shipping, seismic surveys, and offshore development on marine ecosystems and implement effective conservation measures.

Passive acoustic monitoring (PAM) offers several advantages in environmental research, including its ability to operate remotely and continuously, providing long-term data on marine ecosystems. Additionally, PAM is non-invasive, making it ideal for studying elusive or sensitive species without disturbing their natural behavior. It also enables researchers to monitor large areas of the ocean cost-effectively.

Passive acoustic monitoring (PAM) is extensively used in marine mammal research to study the vocalizations, migration patterns, and social behavior of whales, dolphins, and other cetaceans. By analyzing the acoustic signals emitted by these animals, researchers can gain insights into their population dynamics, communication systems, and responses to environmental changes, aiding conservation efforts.

Passive acoustic monitoring (PAM) technology has diverse applications beyond marine biology, including hydrocarbon exploration, offshore wind farm development, and naval surveillance. In hydrocarbon exploration, PAM is used to detect the sounds of marine mammals and mitigate the potential impacts of seismic surveys on these species. Similarly, PAM helps assess the environmental impact of offshore wind farms by monitoring the presence of marine mammals and mitigating collision risks. Additionally, PAM is employed in naval surveillance for detecting and tracking submarines and other underwater threats using acoustic signatures.

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