Reducing Ocean Noise Pollution: Strategies For A Quieter Ocean

Human-generated noise pollution is threatening marine life in our oceans, with potentially negative consequences for our ecosystems. Most marine animals rely on sound for survival, but human-made noise is drowning out their natural soundscape. Sources of marine noise pollution include shipping vessels, seismic surveying for oil and gas, offshore wind farm production, naval sonar training, and construction. To reduce ocean noise pollution, researchers and advocates propose solutions such as redesigning ship propellers, installing acoustic curtains, implementing speed limits and rerouting ships away from sensitive areas, adopting alternative technologies for seismic surveys, and strategically managing water traffic. Addressing ocean noise pollution is crucial for protecting marine life and maintaining the health of the global ocean soundscape.

Reduce shipping noise

Shipping noise is the most pervasive human-generated noise in the ocean and, therefore, a good place to start tackling the issue of ocean noise pollution.

Redesigning ship propellers

Redesigning ship propellers to reduce cavitation can lower the volume of noise emitted by ships. Cavitation is the formation and implosion of water vapour cavities resulting from pressure variations during water movement across a propeller blade. It is the main cause of underwater noise on the loudest vessels. Redesigning propellers to reduce cavitation can lead to a quieter and more energy-efficient ship.

Acoustic curtains

Installing acoustic "curtains" such as bubble curtains can lower the volume of noise emitted by ships. Bubble curtains work by blowing a wall of air bubbles that absorb and refract the noise, reducing it by as much as 15 dB, which amounts to a reduction in acoustic energy of about 95%.

Slow steaming

Practising slow steaming on busy shipping routes can also help reduce noise. Sea transportation companies have found direct linkages between speed and noise. By reducing the speed of ships, the broadband acoustic footprint produced by the fleet can be lowered by approximately 50-65%. Reducing vessel speed also has the added benefit of reducing emissions of greenhouse gases and other air pollutants.

Energy-saving devices

Energy-saving devices (ESDs) can be attached upstream of the propeller to improve its internal efficiency and reduce propeller loading, meaning less cavitation.

Ship design

Engineers can also work on the overall ship design, engines, and equipment from an environmental protection perspective. This includes modifying the hull design to increase the flow into the propeller, thus raising efficiency while reducing cavitation.

Green engineering

During new vessel construction, engineers can transform or adapt all machinery and equipment to become more sustainable and silent. This includes engines, hydraulic systems, ventilation, and pumps.

Reduce oil and gas exploration noise

Oil and gas exploration is a significant contributor to ocean noise pollution, and there are several ways to reduce the noise generated by these activities. Firstly, one of the most effective ways to reduce noise from oil and gas exploration is to implement noise barriers and enclosures. Natural gas plants, for example, often have compressors that emit significant noise, and noise barriers or enclosures can help limit this noise by disrupting or absorbing sound waves. These enclosures require careful maintenance and ventilation to ensure effective noise attenuation.

Another way to reduce noise in the oil and gas industry is to install silencers. Silencers are used to break up high-temperature and high-velocity gas as it leaves a pipe system, gradually lessening its pressure and reducing the noise it creates. Additionally, new noise-mitigating parts and policies, such as changing compressor fan settings, can also help to adjust the emitted sound waves to make them less loud. Regular maintenance of equipment is essential to prevent system complications and increased noise emissions.

Furthermore, oil and gas companies can adopt alternative technologies that produce less noise. For example, seismic surveys, which are used to search for oil and gas reserves, traditionally use airguns that release pulses of low-frequency sound. However, there is a promising alternative called marine vibroseis, which produces less noise while providing equal or better seismic data. By investing in and adopting quieter technologies, oil and gas companies can significantly reduce their noise emissions.

It is also important to consider the impact of noise on nearby residents and the environment. Oil and gas operations near residential areas can cause noise pollution that affects the health and well-being of surrounding communities. To mitigate this, companies can restrict the hours of operation for noise-intensive activities, limit vehicle traffic, and install sound barriers or mufflers to reduce noise levels. By taking these steps, oil and gas companies can reduce their noise footprint and minimize the disruption caused to local residents and wildlife.

Overall, by implementing a combination of noise barriers, enclosures, silencers, alternative technologies, and operational restrictions, the oil and gas industry can significantly reduce its contribution to ocean noise pollution, creating a more harmonious environment for both human and marine life.

Reduce naval sonar training noise

Naval sonar training is a significant contributor to ocean noise pollution. The US Navy, for example, has been granted permission to conduct training exercises that involve "at-sea sonar testing, mine countermeasure and neutralization testing, mine detection and classification testing, kinetic energy weapon testing, propulsion testing, and undersea warfare testing".

These activities have been shown to harm marine life, including whales, dolphins, seals, sea lions, and fish. The noise from sonar can cause whales and dolphins to strand and even die. It can also disrupt their feeding and communication and cause hearing loss.

To reduce naval sonar training noise, the following measures can be implemented:

• Establish a Shipboard Noise Control Team: The team should be led by the Chief Engineer and include the USW Officer, department/division representatives, and technical ratings as required. Their task is to identify noise-generating equipment and develop strategies to minimize noise emissions.
• Identify Installed Systems and Equipment: The team should identify systems and equipment that contribute significantly to the amount of noise generated by the ship. This includes machinery, piping, and propellers.
• Learn About Installed Noise Control Features: Understand how the noise control features on the ship contribute to silencing, such as the Prairie/Masker system and sound isolation devices.
• Establish a Monitoring Program: Conduct periodic surveys of noise-isolated equipment and their isolation devices to prevent degradation of the ship's acoustic signature. This includes internal and external monitoring to identify noise-generating equipment and ensure proper maintenance.
• Develop a Quiet Ship Bill (QSB): This document outlines the optimal equipment lineup and ship speeds to minimize noise emissions. It involves selecting equipment and speeds that reduce cavitation and optimize the ship's noise signature.
• Implement Acoustic Curtains: Install acoustic "curtains", such as bubble curtains, to reduce the volume of noise emitted by sonar.
• Modify Ship Design and Machinery: This includes redesigning ship propellers to reduce cavitation and installing resilient mounts, distributed isolation material, and flexible connections to control noise at its source and during transmission.
• Implement Strategic Traffic Management: Naval forces should coordinate with each other and marine life advocates to reroute ships away from sensitive areas and feeding grounds of marine life, especially endangered species.
• Incentivize Alternative Technologies: Encourage the use of quieter technologies, such as marine vibroseis for seismic surveys, by providing economic incentives or incorporating it into regulatory requirements.
• Restrict Activity in Certain Areas: Implement spatiotemporal restrictions on naval sonar training activities, such as avoiding biologically sensitive areas during fish spawning seasons or halting activities if marine life is detected within a certain radius.
• Incorporate Noise Pollution in Environmental Assessments: Include noise pollution as a factor in environmental impact assessments to ensure that the potential harm to marine life is considered alongside other physical stressors like chemical pollution and climate change.

Reduce construction noise

Construction noise is one of the many human-generated sources of ocean noise pollution. This noise pollution has been found to negatively impact marine life, which relies on sound for survival.

To reduce construction noise in the ocean, here are some measures that can be implemented:

• Use of acoustic curtains: Installing acoustic or "bubble" curtains around construction sites can help to dampen the noise created by pile-driving and other construction activities. These curtains are made of perforated pipes that release air bubbles to absorb and refract the sound, reducing its impact on the surrounding marine life.
• Alternative construction methods: Finding alternative construction methods or foundations can help reduce noise pollution. For example, instead of using pile-driving, floating bases or other alternative foundations can be considered for structures like offshore wind farms.
• Improved planning and impact assessments: Construction noise can be reduced by carefully planning the placement of structures and conducting thorough environmental impact assessments. This includes considering the location of sensitive marine habitats and species when deciding where to place wind turbines or other structures.
• Regulatory and policy changes: Implementing and enforcing regulations and policies that address construction noise can be effective. This includes setting decibel limitations, especially in areas with vulnerable marine habitats, and creating guidelines for construction practices to minimize noise pollution.
• Incentivizing quieter practices: Providing financial incentives or subsidies for companies that adopt quieter construction practices can encourage the use of alternative methods and technologies to reduce noise emissions during construction.
• Collaboration and education: Educating the public about the impacts of construction noise on marine life and engaging with stakeholders can help build support for noise reduction measures. Collaborating with international bodies, governments, and non-governmental organizations can also lead to the development and implementation of effective policies and regulations to address construction noise in the ocean.

By implementing these measures, it is possible to reduce construction noise in the ocean, contributing to the protection and conservation of marine ecosystems and the species that rely on them.

Implement noise-reducing technologies

Implementing noise-reducing technologies is crucial to mitigate the harmful effects of ocean noise pollution on marine life. Here are some detailed strategies and their potential impact:

Redesigning Ship Propellers:

Modifying ship propellers to reduce cavitation can significantly decrease noise levels. For example, the Danish shipping company Maersk spent over $100 million in 2017 to retrofit vessel hulls and install more efficient propellers, resulting in a noise reduction of 6 to 8 decibels, or a 75% reduction in acoustic energy.

Acoustic Curtains and Barriers:

Installing acoustic "curtains," such as bubble curtains, can effectively dampen noise during construction and other underwater activities. For instance, at offshore wind farms, acoustic bubble curtains have been used to reduce noise by up to 15 decibels, which translates to a 95% reduction in acoustic energy.

Quieter Seismic Surveying:

Traditional seismic surveying for oil and gas exploration uses airguns that release pulses of low-frequency sound, causing auditory damage and increased mortality among marine life. A promising alternative is marine vibroseis, a quieter technology that produces equal or better seismic data. This method generates less harmful frequencies, reduces surveying time, and lowers overall sound pressure levels.

Ship Speed and Route Optimization:

Slowing down ships and rerouting them away from sensitive marine ecosystems can help lessen the impact of shipping noise. For example, in Glacier Bay National Park, studies found that reducing cruise ship speeds or scheduling ships to arrive at hourly intervals decreased underwater noise levels and created quieter periods, benefiting whale communication and behaviour.

Electrifying Ships:

While this strategy is still in its early stages, electrifying ships has the potential to significantly reduce noise pollution caused by ship propellers.

Frequently asked questions