The Noise Problem Nobody Talked About
For years, if you wanted to move a small boat through the water, you had two choices. Paddle, or burn fuel.
Paddling was quiet but tiring. Burning fuel was powerful but loud—and not just above the water. Underneath, where fish live and marine mammals communicate, the noise from a combustion engine travels far and disrupts everything it touches.
That trade-off is finally disappearing.
A landmark peer-reviewed study published in the Journal of the Acoustical Society of America has given the 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 43 Decibels Actually Means
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.
Even at higher speeds where cavitation becomes a factor for both propulsion types, the electric system maintained a measurable noise advantage across the entire tested speed range from 4 to 20 knots .
Why This Matters for Anglers and Wildlife Observers
For anyone who spends time on the water with the goal of observing wildlife or catching fish, noise is not just a "nice to have" feature. It is often the difference between success and failure.
For fishing: Fish are sensitive to vibrations and sound. A loud motor announces your arrival long before you reach your fishing spot. The fish scatter. The bite stops. Quiet propulsion changes that. You can approach fishing grounds without spooking the fish, giving yourself a real advantage .
For wildlife observation: Companies like Pangolin Photo Safaris in Botswana have switched to electric propulsion specifically to get closer to wildlife on the Chobe River . The same principle applies to whale watching, dolphin observation, and any marine research that requires getting near animals without disturbing them.
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.
Some systems produce significant underwater noise at higher frequencies, making them increasingly audible to species with good high-frequency hearing, including porpoises . Careful motor and power electronics design is essential to achieving true quiet operation.
What This Means for Your Build
Whether you are setting up a kayak for fishing, a small boat for coastal exploration, or an ROV for marine research, noise should be a primary consideration in your propulsion choice :
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Low-speed operation matters most. The 43 dB reduction was measured at 4 knots—exactly the speed range where most small watercraft operate near shorelines and sensitive areas.
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Brushless motors are key. Brushless technology eliminates the noise and wear of brushed motors, contributing to quieter, more efficient operation .
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Integration reduces noise. A well-integrated propulsion system with quality bearings and precision-balanced components runs smoother and quieter than a cobbled-together setup.
The Bigger Picture
The 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.
RAD co-founder Dan Hook put it this way: "Low frequency noise from engines can travel a long way underwater and upset marine wildlife, so we have put a lot of effort into selecting the right type of motor and mechanics to minimise that" .
The same principle applies to any electric propulsion system designed for quiet operation.
Quiet Propulsion Is Becoming a Requirement, Not a Luxury
For years, "quiet" was a marketing claim. Now it is backed by peer-reviewed science. The message is clear: the marine industry is moving toward quieter propulsion, and the technology is here to support it.
Whether you are a kayak angler, a paddle boarder, or a marine researcher, the ability to move through the water without announcing your presence changes what is possible on the water. And that changes everything.
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