How bubble curtains and MNRU protect marine life

Underwater noise pollution from offshore wind construction 

Offshore wind farms are key to a sustainable future; however, their construction can bring several environmental challenges. Underwater noise pollution is a growing concern in the industry, significantly impacting marine life. Effective noise mitigation solutions are essential. In this blog, we explore how bubble curtains and the Menck Noise Reduction Unit (MNRU) offer innovative ways to reduce noise and support eco-friendly offshore construction.  

What are bubble curtains and why they matter 

Bubble curtain technology has been widely used in offshore construction for many years for underwater noise abatement and controlling debris in the water column. They play an integral role in protecting marine life from the harmful noise levels that can disrupt the communication, navigation, and feeding patterns of marine mammals.  

This technology operates by generating a vertical barrier of bubbles, achieved through the release of compressed air via perforated hoses positioned on the seabed. The bubble curtain effectively scatters and absorbs sound waves, thereby reducing noise pollution. Additionally, it offers debris control, making it a valuable asset for marine conservation efforts.  

Advancements in bubble curtain design: "designed bubbles" 

While bubble curtain technology is already widely recognised as one of the key tools for underwater noise mitigation, our future ambition is to take one step further and create designed bubbles. These precisely controlled bubble formations could be shaped and directed much like how Hollywood choreographs fire and smoke effects on set. This advanced control would allow for more effective and targeted noise reduction, adapting in real-time to specific tools, environmental conditions, and project needs.   

However, reaching this level of sophistication comes with its challenges: ensuring hose stability on the seabed, maintaining consistent systems performance, and optimising efficiency in different water conditions remain some of the technical hurdles. At Acteon, our engineers are actively developing innovative solutions, including next-generation hose designs, modular yet capable winch designs and high-efficiency compressors that reduce operational costs, environmental footprint and improve operational safety.  

MNRU: enhancing noise mitigation 

MNRU plays a pivotal role in our overall underwater noise mitigation strategy. It works seamlessly alongside near-field as well as far-field noise abatement systems, such as bubble curtains, providing a layered and highly effective noise reduction solution. As part of the integrated design approach, the MNRU is not merely an add-on but requires careful coordination with the entire noise mitigation setup to maximise performance for each project. This ensures that all elements, from pile hammer to the acoustic barrier, function together for maximum efficiency in reducing noise emissions and protecting marine ecosystems from the harmful effects of underwater noise.  

Technical benefits of MNRU 

MNRU precisely influences the force-generation characteristics of each individual hammer blow during pile driving. By shaping the energy transfer, we can achieve a reduction in noise levels of 9-12 dB, equivalent to more than 80% reduction compared to conventional systems. Beyond noise reduction, this controlled impact approach lowers dynamic stress on the pile, minimising fatigue and opening new opportunities for optimised foundation designs, as well as reducing material usage and construction costs.  

Environmental and economic advantages 

Deploying bubble curtains and MNRU brings dual benefits: 

• Environmental: Significantly reduces underwater noise, minimising disruption to marine life and promoting healthier aquatic ecosystems.
• Regulatory and Economic: Helps developers meet stricter environmental regulations, lowers permitting risk, and boosts public acceptance for offshore wind and marine construction projects. 

Future outlook: quiet oceans & thriving marine life 

Implementing innovative noise mitigation technologies like bubble curtains and the MNRU is vital for safeguarding marine ecosystems from the effects of underwater noise pollution. As we continue to refine and develop these technologies, we can look forward to a future where marine life thrives in quieter, healthier oceans, ensuring a harmonious balance between human activities and environmental conservation.