The Sound of the Sea: Mapping Britain’s Underwater Noise Pollution

When we look out over the British coastline, we tend to think of the ocean as a “silent world.” Aside from the crashing of waves or the cry of a seagull, the depths appear tranquil. However, beneath the surface, the UK’s coastal waters are a cacophony of sound. From the rhythmic clicking of snapping shrimp to the low-frequency thrum of massive container ships, the “soundscape” of the sea is as busy as any motorway.

As part of the GB Row Challenge, teams are rowing 2,000 miles around Great Britain, acting as a silent ears for the ocean. By using specialized underwater microphones called hydrophones, these rowing boats are creating the first-ever continuous acoustic map of the British coast.

Why Sound Matters Under the Waves

For marine life, sound is everything. Light does not travel far underwater, meaning sight is often useless for navigation, hunting, or communication. Instead, marine animals have evolved to “see” with their ears.

• Cetaceans (Whales and Dolphins): Use echolocation to find prey and complex songs to communicate with pods across hundreds of miles.
• Fish: Many species use grunts or “drums” to attract mates or defend territory.
• Invertebrates: Even tiny larvae use the sound of a healthy reef to find a place to settle and grow.

When we introduce “anthropogenic” (human-made) noise into this environment, we aren’t just making it loud; we are effectively blinding the residents of the ocean.

The Invisible Threat: What is Noise Pollution?

Underwater noise pollution is a growing environmental crisis. Because sound travels four times faster in water than in air—and much further—noise from a single ship can be heard for miles. The GB Row research focuses on two main types of noise:

Continuous Noise

This is the “background hum” of the ocean. It primarily comes from the propellers and engines of shipping traffic. For a dolphin, this is like trying to have a conversation while standing next to a running jet engine. It leads to “masking,” where the animal can no longer hear the subtle cues it needs to survive.

Impulsive Noise

These are short, incredibly powerful bursts of sound. Examples include pile-driving for offshore wind farms, seismic surveys for oil and gas, or sonar from naval vessels. These sounds can be physically damaging, causing permanent hearing loss or even death in marine mammals.

The Rowing Boat: The Perfect “Quiet” Platform

Measuring noise pollution from a standard research vessel is notoriously difficult. The ship’s own engine and the “cavitation” (bubbles) created by its propellers contaminate the recordings. It is like trying to measure the noise of a library while shouting.

This is where the GB Row boats offer a massive scientific advantage. A rowing boat is almost entirely silent. Driven by human power, it glides through the water without an engine. This allows the hydrophone—mounted securely to the rudder or hull—to capture the true, untainted soundscape of the British coast.

Moving at a slow, steady pace, the rowers provide a high-fidelity “long-form” recording. As they pass through the busy waters of the English Channel and move into the remote Scottish Minch, they document the dramatic shift in acoustic health across the UK.

Turning Sound into Data

As the teams row, the hydrophone converts pressure waves in the water into digital signals. This data is stored on ruggedised hard drives on board and later analysed by experts at the University of Portsmouth.

Scientists look for several key indicators:

• Sound Pressure Levels (SPL): How loud is the ocean at different points around the coast?
• Frequency Distribution: Are the noises high-frequency (like jet skis) or low-frequency (like tankers)?
• Biological Activity: Can we hear the “bio-acoustic” signature of a healthy ecosystem, such as snapping shrimp or whale clicks, amongst the human noise?

By comparing these recordings with the eDNA samples (which identify which species are present), researchers can see if high noise levels are driving certain animals away from their natural habitats.

Protecting the Future of the UK Coastline

The ultimate goal of mapping Britain’s underwater noise is to influence policy. The data collected by GB Row is uploaded to the Marine Data Exchange, providing a vital resource for the government and offshore developers.

If we can identify “noise hotspots,” we can implement better management strategies, such as:

• Slowing down shipping traffic in sensitive areas (which significantly reduces noise).
• Using “bubble curtains” during offshore construction to dampen the sound of pile-driving.
• Designing quieter propeller technology for commercial vessels.

Frequently Asked Questions

Can you hear the rowers rowing?

Occasionally, the hydrophone picks up the rhythmic “clunk” of the oars in the rowlocks or the splash of the blades entering the water. However, these are very low-impact sounds compared to a motorised engine and are easily filtered out during analysis.

What is the loudest thing you’ve recorded?

Large commercial shipping vessels and nearby construction work are consistently the loudest sources. In some areas, the background “hum” of the ocean is now several decibels higher than it was just a few decades ago.

How far away can the hydrophone “hear”?

Depending on the water conditions and the depth, the hydrophone can pick up large ships that are over 20 miles away. It can also detect the high-frequency clicks of a dolphin within a few hundred metres.

The GB Row Challenge proves that to save our seas, we first need to listen to them. As the 2026 teams pull their oars through the water, they are helping us understand the silent struggle of marine life, ensuring that the “Sound of the Sea” remains a song of nature, rather than a roar of industry.