Ocean Noise

Studying noise provides critical information about ocean species and ecosystems, and how they may change in time due to natural processes and climate change.

For marine ecosystems: Many marine species rely on sound for communication, orientation, and navigation. They can be stressed and change behaviour in response to increased noise levels, or may even suffer physical harm from noise.

For ocean physics: Noise analysis helps us understand physical oceanography and ocean dynamics in coastal, pelagic, and deep-sea regions, and provides evidence of climate variability.

For unique fingerprinting: Noise analysis in space and time provides an opportunity for unique fingerprinting of diverse processes, and for understanding how our oceans are evolving from natural and human-induced factors.

Without this research, we'd lose crucial insights into ecosystem health, ocean processes, and the impacts of human activities on marine environments.

The ocean soundscape is changing in response to numerous human activities:

Resource extraction and offshore infrastructure development:

• Fishing, mining, and drilling operations
• Marine infrastructure and construction
• Geophysical exploration and seafloor mapping
• Oil and gas production

Energy generation:

• Tidal and wave energy converters
• Offshore wind farms (both construction and operation)

Storage activities:

• CO₂ sequestration
• Hydrogen storage

Other sources:

• Vessel traffic
• Explosions and nuclear ordnance

Some anthropogenic noise sources are short-duration, such as explosions, whilst others occur over long periods of time, such as vibrations linked to the operation of wind farms.

Whether short-duration or long-lasting, human-induced noise can cause serious impacts on marine life, particularly marine mammals:

Physical damage: High-intensity sounds can cause physical injury to sensitive hearing organs.

Stress: Chronic exposure to elevated noise levels causes physiological stress.

Behavioural changes: Animals may avoid important habitats, alter migration routes, or change feeding patterns.

Reduced reproductive success: Noise interference with communication can affect mating and parenting behaviours.

Communication masking: Background noise can prevent animals from hearing important signals from conspecifics or their environment.

These impacts highlight why efforts for a sustainable blue economy must prioritise understanding the impact of human-induced noise across the ocean, to define safe noise level and noise duration recommendations, and guide noise mitigation schemes.

We record noise with a variety of marine sensors, each capturing different aspects of the acoustic environment:

Hydrophones: Record changes in pressure, which includes sound waves travelling through the water column. These capture acoustic signals in the water.

Ocean Bottom Seismometers (OBS) and Ocean Bottom Nodes: House geophones that record seismo-acoustic signals received at the seafloor across three directions, capturing both seismic and acoustic energy.

Distributed Acoustic Sensing (DAS): Captures deformation along seafloor cables caused by vibrations. This emerging technology turns fibre-optic cables into dense arrays of acoustic sensors.

The deployment and recovery of these instruments usually require seagoing expeditions, and the design of such surveys is guided by initial modelling studies to best capture the noise.

Our research focuses on ocean noise investigation across a broad frequency range, from tens of millihertz to kilohertz, enabling us to study phenomena at vastly different scales:

Ultra-low frequencies (millihertz): Gravity waves, tsunamis, tides, and large-scale ocean circulation patterns.

Low frequencies (Hz): Microseisms from wind-ocean interactions, earthquakes, volcanic activity, and shipping noise.

Mid frequencies (tens to hundreds of Hz): Marine mammal vocalisations, internal waves, and anthropogenic sources like construction.

High frequencies (kHz): Sounds from smaller marine life (crabs, shrimp), rain, bubbles, and high-resolution acoustic imaging.

This broad frequency coverage allows us to capture the full spectrum of ocean processes and their interactions.

Ocean noise research provides essential information for sustainable ocean management:

Regulatory frameworks: Data on noise levels and impacts inform development of noise regulations and guidelines for marine industries.

Marine Protected Areas: Acoustic monitoring ensures MPAs are genuinely protecting marine life from noise pollution, detecting unauthorised vessel traffic and industrial activities.

Environmental impact assessments: Baseline noise measurements and impact predictions guide decisions about offshore development projects.

Mitigation strategies: Understanding noise propagation and impacts enables design of effective mitigation measures, from seasonal restrictions to technological solutions.

Monitoring compliance: Ongoing acoustic monitoring verifies that industries are operating within permitted noise levels.

This evidence-based approach supports a sustainable blue economy that balances economic development with ecosystem protection.

Acoustic monitoring has important applications for maritime security:

Vessel detection: Passive acoustic monitoring can detect and classify vessels, including submarines, without active sonar that might disturb marine life.

Navigation safety: Understanding the acoustic environment improves sonar performance and helps vessels navigate safely.

Underwater surveillance: Monitoring networks can provide awareness of activity in sensitive maritime zones.

Treaty verification: Acoustic networks can detect underwater explosions, supporting nuclear test ban treaty monitoring.

These applications demonstrate how fundamental research in ocean acoustics serves both scientific and societal needs.