The not-so-silent world: monitoring underwater noise using non invasive techniques

For a long time, the prevailing notion was that the ocean was a place devoid of any sound. The idea gained prominence with Jacques Cousteau’s book (1953) and documentary (1956) of the same title “Silent World,” which provided a captivating glimpse into the marine environment, but overlooked its rich acoustic environment. We now know the ocean is filled with myriad sounds originating from diverse sources such as animal vocalizations, physical phenomena like rain, wind, and earthquakes, as well as human activities including vessel traffic, military sonar, and resource exploration. Increasing evidence demonstrates that a multitude of marine life rely on sound for survival.  

The ocean soundscape 

The characterization of all the acoustic sources present in a certain place is known as the “soundscape” of an ecosystem. Scientists around the world are recording underwater sounds to learn more about the ocean soundscape. The study of underwater soundscapes not only provides valuable insights into the ocean’s acoustic environment and levels of underwater noise, but also yields crucial biological information regarding species’ habitat use, abundance, distribution, density, and behaviour. These findings can be linked to ecosystem health assessments and other bioindicators. 

What is Passive Acoustic Monitoring?

Passive Acoustic Monitoring (PAM) is a non-intrusive technique that involves the deployment of cabled hydrophones (underwater microphones), autonomous recorders, or towed hydrophone arrays, to monitor both animal sounds and environmental noise in the marine environment. PAM methods have several advantages over traditional visual surveys, as they enable the acoustic detection of animals consistently throughout the year, even in remote locations and unfavorable visibility or weather conditions, providing valuable data on species ecology and evolving soundscapes across diverse spatial and temporal scales.   

PAM methodologies have developed significantly over the past two decades, leading to their widespread use by an unprecedented number of individuals and organizations. To celebrate the increasing use of PAM around the world and to help bring awareness to acoustic ecosystems, today, June 8, will celebrate the first World Oceans Passive Acoustic Monitoring Day (WOPAM) on World Oceans Day.

Current monitoring on the west coast

Stretching from Alaska to Washington State, the west coast harbors a remarkable network of waterways. Along this awe-inspiring coastline, numerous organizations are finely attuned to the sounds of the sea, employing PAM techniques to monitor and unravel its soundscapes. 

Despite the number of hydrophones currently in the water, the task of effectively comparing these data possess a real challenge. Each piece of equipment is calibrated differently, and the perceived noise levels can be affected by an array of  factors including placement depth, viewing angle and the composition of the seafloor. Even minute variations in water temperature can affect the way that soundwaves travel through water and are received by monitoring equipment!

An integrated underwater noise monitoring initiative for British Columbia 

Raincoast is currently piloting an ambitious new initiative known as NoiseTracker, which aims to establish a collaborative network of hydrophone operators joined in a common effort to comprehensively monitor underwater noise in BC. Our vision is to create a centralized platform  to present noise data in a congruent and standardized manner. We are aiming to build a website that can be used by members of the public, researchers, and environmental stewards to monitor and track trends in ocean noise, with a goal to inform successful mitigation policies coastwide. In addition, we are strategically deploying two hydrophones of our own on Pender Island and the Sunshine Coast. 

Through these monitoring stations, we aim to gain valuable insights into habitat use and potential interactions with vessels for the endangered Southern Resident killer whales and migratory baleen whales that frequent these coastal areas. A multitude of species that inhabit our waters are highly sensitive to elevated noise levels, and it is our shared responsibility to protect them. 

Learn more

This World Oceans Day, we encourage you to learn more about Passive Acoustic Monitoring as a tool for understanding and conserving our incredible oceans! To learn more about underwater sounds and the many ways animals use them, visit the Discovery of Sounds in the Sea website.

You can help

Raincoast’s in-house scientists, collaborating graduate students, postdoctoral fellows, and professors make us unique among conservation groups. We work with First Nations, academic institutions, government, and other NGOs to build support and inform decisions that protect aquatic and terrestrial ecosystems, and the wildlife that depend on them. We conduct ethically applied, process-oriented, and hypothesis-driven research that has immediate and relevant utility for conservation deliberations and the collective body of scientific knowledge.

We investigate to understand coastal species and processes. We inform by bringing science to decision-makers and communities. We inspire action to protect wildlife and wildlife habitats.