Noise And Our Fans

April 4, 2020

Brad Marsden

Director - Marine Air Flow International

35 Years Experience in the Marine Industry

Fan Noise Calculations

When you look at a subject such as noise levels, there are a number of ways to measure and/or calculate noise levels.

When we offer you a noise level for one of our fans we do this by supplying your the worst case scenario which is referred to as the Sound Power level "CAUSE" or SWL.

Sound power is the acoustical energy emitted by the sound source (in our case fans), and is an absolute value. It is not affected by the environment. Sound power levels are connected to the sound source and are independent of distance.

The other common way to show sound levels is called sound pressure often referred to as SPL. This is what a lot of Fan Manufacturer's use as their reference to sound levels. Sound pressure is a pressure disturbance in the air whose intensity is influenced not only by the strength of the source, but also by the surroundings and the distance from the source to the receiver. Obstacles and barriers such as air ducts, air absorption from lagging and insulation, wind as well as other factors are taken into account. So any acoustic paint, insulation, sound attenuaters that you may install on the application to reduce noise will factor into this reading.

Sound pressure is what our ears hear and what sound pressure level meters (SPL meters) measure.

This measurement looks a lot better on the data sheet but can be deceiving as the only way to 100% guarantee this level is to measure the reading in the exact same in environment. We would have to be in the same size area, of the exact same constuction with the exact same components inside the measurement area. In practical terms for an engine room, it would have to be the same size, shape, construction, have the same aluminium duct's, the same intake separator grilles in front of the fan, the same lagging and insulation and the list goes on.

So you can see that the SPL measurement is impossible to state with regards to accuracy. The best way is to provide you with a SWL as that will be accurate no matter the situation.

To give you more of an understanding about this we have done two performance graphs of the same impeller/motor assembly.

Option 1 is the Sounds Power (How MAFI will measure sound for you) & Option 2 is the Sound pressure as supplied regularly by manufactures.

You will note that the MAFI sound level is not nearly as low and therefor not so attractive, however it is the most accurate measurement of worst case scenario. Once you install all of your acoustic barriers it a more realistic level of outcome.

We would strongly recommend avoiding the use of sound pressure levels as it will generally lead to disappointment. These levels can be out by 10-15% once installation has occured.

Of course any questions, please get in touch with Brad or Mark who will be able to chat to you about how noise levels relate to your specific application.

Sound Power Graph (As MAFI will supply)

Sound Pressure - As often supplied by manufacturers

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56 Meter RORO Ferries Project For Abu Dhabi

By Brad Marsden • June 10, 2025

Optimising Engine Room Ventilation for Abu Dhabi’s High-Speed Ro-Pax Ferries As part of Abu Dhabi’s ongoing investment in advanced maritime infrastructure, the AD Ports Group commissioned two high-speed Ro-Ro ferries to operate between the UAE mainland and Delma Island. Carrying 250 passengers and 25 cars per trip at a service speed of over 30 Knots is pretty impressive , and you'd have to agree they are certainly very tidy looking Roll On Roll Off Ferries!! Designed for both passenger comfort and operational performance, these cutting-edge vessels required a ventilation solution that could meet the rigorous demands of the Gulf’s climate and the intense operating conditions of four powerful MTU engines per vessel. Our team was proud to be selected to design and deliver the engine room ventilation system for these state-of-the-art ferries, ensuring they remain safe, efficient, and reliable at sea. Engineering the Future of Fast Ferry Travel Built to carry up to 194 passengers and 25 vehicles, each of the 56-metre-long catamarans has been equipped with four MTU 16V4000M65L high-performance engines driving Kongsberg KaMeWa waterjets. This powerful propulsion setup enables cruising speeds of up to 35 knots, making the ferries among the fastest in their class within the region. Inside, the vessels feature modern amenities such as a VIP lounge, children’s play area, two cafes, five toilets, and full wheelchair accessibility, highlighting AD Ports Group’s commitment to both efficiency and passenger experience. Operating in the heat of the Persian Gulf, however, presents unique engineering challenges. The heart of this lies within the engine room where temperatures, airflow, and safety systems must be tightly controlled to prevent overheating, ensure compliance, and protect both crew and machinery. A Tailored Ventilation Solution for Demanding Conditions The brief for this project was clear: create a ventilation system that could not only manage the extreme thermal loads generated by four high-output marine engines but also comply with international marine safety standards, including fire isolation and redundancy protocols. Key features of the system we delivered include: Marine-Grade Ventilation Dampers : Built from corrosion-resistant stainless steel, our dampers are designed for longevity and reliability in a saltwater environment. Integrated Auto Close Capability : The dampers are configured to close rapidly in the event of a fire, helping to isolate the engine room and restrict oxygen supply. High Airflow Capacity : Designed specifically for the compact, high-output layout of the engine rooms, the system allows for maximum airflow and heat dissipation under full load. Moisture and Salt Mist Defence: Our Intake grilles are known globally for their excellent capability of reducing salt mist and spray into your engine room. Here they allow a vessel operating in already extreme conditions to require far less ongoing equipment replacement. Redundancy & Safety : With automated control options and manual overrides, the system ensures continuous operation and safety during engine shutdowns or emergencies. Delivering Results at Sea With the ventilation system now fully installed and operational, the Ro-Pax ferries have successfully completed sea trials and are ready to begin service. The performance of the engine room ventilation under load has exceeded expectations, maintaining optimal operating temperatures even during high-speed runs in the peak Gulf heat. In addition to thermal performance, the system’s fire isolation capability offers an added layer of safety, helping these ferries meet stringent international compliance standards while delivering peace of mind for operators and passengers alike. Reflecting on the Project This project underscores the critical importance of high-performance ventilation systems in modern vessel design. From the intense thermal loads of multi-engine configurations to the need for rapid fire response and corrosion resistance, every detail matters when it comes to marine safety and reliability. We’re proud to have played a key role in supporting this milestone for AD Ports Group and Abu Dhabi’s maritime future and we look forward to bringing this level of engineering excellence to future vessel builds across the region and beyond. Talk to Us About Your Marine Ventilation Needs Whether you’re designing a new-build high-speed ferry or retrofitting an existing vessel, we offer tailored ventilation solutions that combine safety, efficiency, and performance. Get in touch with our team today to learn how we can support your next marine engineering project.