Quiet is not just a feeling. It is a number. And that number is 43.
A landmark peer-reviewed study just published in the Journal of the Acoustical Society of America has given the electric marine industry something concrete to point at. Researchers from University College London's Department of Mechanical Engineering, in collaboration with electric propulsion company RAD, conducted controlled trials comparing an electric outboard with a conventional internal combustion engine of the same power .
The result? At 4 knots—the speed at which many small vessels operate near coastlines, marine reserves, and sensitive habitats—the electric vessel produced broadband source levels 43 decibels lower than the combustion engine vessel .
What does 43 decibels mean?
In acoustic terms, a reduction of 10 decibels is perceived as roughly half as loud. A reduction of 43 decibels is not a small improvement. It is a transformation.
The study also found that electric propulsion eliminates the low-frequency combustion noise that is particularly damaging to species such as baleen whales, which rely on low-frequency hearing for communication and navigation. For these animals, a passing diesel boat is not just an annoyance—it is a wall of sound that can mask their calls from miles away .
Not all electric drives are equal
Here is what makes this study especially interesting. The researchers noted that the high-frequency electrical noise produced by the RAD system was lower than levels reported for other electric propulsion systems in previous studies. The conclusion? How you engineer an electric drive matters enormously. Not all electric motors are acoustically equal .
Why this matters for HobbyWater customers
Whether you are building an ROV for marine biology research, a kayak for quiet fishing, or an autonomous vessel for environmental monitoring, noise is not just a "nice to have" feature. It is often the difference between observing wildlife and scaring it away.
Our TD Series thrusters are engineered with this in mind. Brushless motor technology, precision-balanced rotors, and quality bearings all contribute to quieter operation. Because when you are trying to film a whale shark or monitor a seahorse population, the last thing you want is your own propulsion system announcing your arrival.
The bigger picture
This UCL study is part of a growing body of evidence that electric propulsion is not just cleaner in terms of emissions—it is also quieter in ways that matter to marine life. As more research emerges, we expect to see tighter noise regulations in marine protected areas, national parks, and coastal zones .
The message is clear: Quiet propulsion is becoming a requirement, not a luxury.
Thinking about your next build? Browse our thruster lineup at hobbywater.com, or reach out to discuss which model fits your noise sensitivity requirements. 🌊🔇
