Underwater radiated noise – predict and reduce vessel noise from the design phase
Elomatic Marine predicts and reduces underwater radiated noise for newbuilds and vessels in service. CFD modeling, compliance support, and port incentive assessments.
Underwater radiated noise (URN) is the sound a vessel transmits into the water through its hull. The main sources are propeller cavitation and vibrations from onboard machinery. URN disrupts marine mammals that rely on sound for communication, navigation, and hunting and it is coming under increasing regulatory and commercial scrutiny.
We help shipyards predict and minimize URN during the design phase, and support shipowners with compliance assessments, port incentive scheme evaluations, and operational noise analysis for vessels already in service.
Key Takeaways
- Underwater radiated noise (URN) is sound transmitted through a vessel’s hull into the water, primarily from propeller cavitation and onboard machinery.
- IMO revised its URN guidelines in 2023. Compliance is currently voluntary, but regulations are expected to tighten.
- Port incentive schemes in Vancouver and Prince Rupert already offer reduced harbour fees for low-noise vessels, turning quiet operation into direct financial value.
- We predict URN levels using CFD simulation, enabling noise reduction before a vessel is built.
- Early URN consideration in the design process is significantly more cost-effective than retrofitting later.
Why underwater radiated noise is becoming a priority
IMO guidelines on URN were revised in July 2023 and came into effect on 1 August 2023. While compliance remains voluntary, an IMO experience-building phase is running until 2028, and mandatory measures are widely expected to follow. The EU already monitors continuous underwater noise under the Marine Strategy Framework Directive, with limits on how much of a marine area can be exposed to shipping noise.
Port incentive schemes are already translating noise performance into direct financial value. The ports of Vancouver and Prince Rupert offer harbour fee reductions for vessels that meet low-noise criteria, so quieter vessels can lower their operating costs on these routes.
For shipowners and operators, acting now means lower compliance risk, access to incentive schemes, and vessels better positioned for tightening future requirements.
How we predict and reduce underwater noise
We predict cavitation and underwater noise reliably at the design phase using CFD. The prediction is based on three complementary methods: Detached Eddy Simulation (DES) for turbulence modeling, the Williams-Hawkings equation for far-field noise prediction, and the Schnerr-Sauer model for cavitation simulation. Together, they give a complete picture of the vessel’s noise before it is built.
CFD hydrodynamic modeling
We use CFD to model cavitation, turbulence, and pressure pulses from the propeller and appendages – the primary contributors to URN.
Our simulations cover:
- Noise source prediction: cavitation, turbulence, and pressure pulse modeling validated against experimental data
- Noise radiation simulation: how sound propagates from the vessel into the far field, identifying critical areas for mitigation
- Design optimization: testing propeller shapes, hull modifications, and appendage configurations to find the quietest solution
- Operational analysis: simulating different speeds and operating profiles to identify quieter conditions
Noise emission modeling
In addition to CFD, we carry out simulation and theoretical analysis in noise emission studies. This covers:
- Hydrodynamic noise reduction: optimization of appendages, propellers, including propeller-hull acoustic interaction analysis
- Machinery and component noise reduction: identification of noise from motors, pumps, and piping systems, with design optimization to reduce turbulence-generated noise
CFD allows vessel owners to design ships that meet environmental regulations while improving the health of marine ecosystems by minimizing acoustic disturbances to marine life.
Juha Tanttari, Lead Consulting Engineer, Elomatic
Support for newbuilds and vessels in service
For shipyards, we integrate URN prediction into the design process from the earliest stages. Hull form, propeller geometry, and machinery arrangement can all be evaluated for noise performance before any steel is cut, eliminating the need for costly late-stage modifications.
For shipowners and operators, we assess the URN performance of existing vessels, evaluate eligibility for port incentive schemes, and identify practical measures to reduce noise output on vessels already trading.
Download our comprehensive URN brochure and take the next step towards quieter, more sustainable shipping!
- Advanced noise source analysis and simulation (propulsion, hull, machinery)
- Design solutions that reduce noise without compromising efficiency
- Integration with energy-saving and emission-reduction strategies
Frequently asked questions
The main source is propeller cavitation: bubbles that form and collapse around the propeller blades generate broadband noise. Engine and machinery vibrations transmitted through the hull into the water are the second major source, contributing low-frequency noise. Appendages and hull form also affect the overall noise signature.
Currently there are no mandatory global URN regulations for commercial shipping. The IMO guidelines, revised in 2023, are voluntary. The EU monitors continuous underwater noise under the Marine Strategy Framework Directive. Mandatory requirements are expected to develop from the IMO experience-building phase, which runs until 2028.
CFD simulates the flow around the propeller and hull, predicting where cavitation and turbulence will occur and how much noise they generate. Different design alternatives can be tested in simulation before any hardware is built. This allows noise to be engineered out at the design stage, significantly reducing the need for expensive post-build modifications.
Yes. For existing vessels, we assess current noise performance, model the impact of potential modifications such as propeller replacement or appendage changes, and identify the most effective measures. Retrofitting is more costly than designing for low noise from the start, but meaningful reductions are achievable on vessels in service.
The ports of Vancouver and Prince Rupert in Canada currently offer port fee reductions for vessels meeting URN thresholds. The number of ports with such schemes is growing. We can assess whether your vessels qualify for existing schemes and model the potential financial benefit across your trading routes.
Want to know how quiet your vessel is — or could be?
Tell us about your project and we will outline what URN analysis can tell you.
